As part of my research, I tried the Protocentral_ADS1220<\/a> library. It is slim and basically it works well, except for one of the two example ketches. However, when testing various settings, I often had to refer to the ADS1220 data sheet or look for the parameters for the functions in the header file. Therefore, I have written the library ADS1220_WE. It is an attempt to make the operation of the ADS1220 comfortable. You can find my library here<\/a> on GitHub or install it using the Arduino library manager. Try both and choose the one you like best.<\/p>\n\n For the connection of the ADS1220 to a microcontroller, the data sheet<\/a> in section 9.1.1 recommends the use of some capacitors and resistors. If you want it simple, like I do, use a module that already has these additional components implemented. You can get such a module in online stores for less than 10 Euros, mostly directly from China.<\/p>\n Key technical data are:<\/p>\n The labels of the inputs and outputs on the module partly differ from the data sheet (in brackets, if different):<\/p>\n\n I will explain how to use the ADS1220 with example sketches. First, I want to show you how to change input channels and query data using the default settings. For my example sketch, the following circuit was used:<\/p>\n\n The manufacturer of the ADS1220 recommends using 47 \u03a9 resistors between all digital inputs and outputs and the microcontroller. It also recommends using 0.1 F capacitors between AVDD and GND and between DVDD and GND. CLK should be connected to GND. You can find more detailed information on this in section 9.1.1 of the data sheet. <\/p>\n The ADS1220 modules I have do have 24 \u03a9 resistors in front of MOSI, CS, and SCLK. Why this size? I don’t know. Theoretically, you would need to add 23 \u03a9 resistors there and install 47 \u03a9 resistors on MISO and DRDY. Capacitors are obviously located on AVDD and DVDD, but I don’t know if they have the recommended capacity. CLK is connected to DGND via a 10 k\u03a9 resistor. So you don’t need to worry about that. <\/p>\n Unused analogue inputs\/outputs should be connected to AVDD or (AVDD+AVSS)\/2. Exception: AIN3\/REFN1. Unused digital inputs should be connected to DVDD or DGND. Exceptions: CLK \u2013 DGND only; DRDY \u2013 leave unconnected or HIGH via pull-up resistor. <\/p>\n\n The module I used has two 0 \u03a9 resistors that connect DGND and AGND or DVDD and AVDD. In this respect, I could have saved two connections above. If you need different voltages for the digital and analog pins, then remove at least the resistor that connects DVDD to AVDD, and possibly also the second one (e.g. with a bipolar power supply). <\/p>\n\n In this example, the internal voltage reference of 2.048 volts is used. This means that you can only measure voltages in the range of -2.048 to +2.048 volts.<\/p>\n The output voltage of the PGA must be greater than AVSS plus 200 millivolts and lower than AVDD minus 200 millivolts. Outside these limits, the ADS1220 no longer operates linearly. As the standard gain is 1, these limits also apply to the input voltage in the first example. To be on the safe side, we turn off the PGA with The measured voltage is calculated from the raw value as follows, taking into account the amplification factor and the reference voltage:<\/p>\n\n <\/p>\n <\/span> <\/span> Here’s the sketch:<\/p>\n<\/p>\n \u00a0<\/p>\n<\/div>\n \n\n I only go into the parts that, I think, need explanation (otherwise, ask!):<\/p>\n This is how the output of the sketch may look like:<\/p>\n As you can see,VAIN0\/AIN1<\/sub> = (VAIN0\/AVSS<\/sub> –VAIN1\/AVSS<\/sub>), which must be the case on closer inspection.<\/p>\n\n As mentioned before, you have four options for the reference voltage:<\/p>\n The following circuit diagram is intended to illustrate this:<\/p>\n\n I used the circuit shown above and applied different reference voltages to REFP0\/REFN0 and REFP1\/REFN1. A test voltage to be measured was connected to AIN2.<\/p>\n The following sketch shows how to set or change reference voltages for the ADS1220:<\/p>\n<\/p>\n \u00a0<\/p>\n<\/div>\n \n\n This is what the output looked like for me:<\/p>\n By default, the ADS1220 uses the internal reference voltage. If you want to switch to an external reference voltage, you have two options:<\/p>\n The ADS1220 data sheet states that the external reference measurement is less accurate than a regular measurement. One should not overestimate this error, because the internal reference voltage also has a certain error (up to 3 millivolts). However, I would not call the functions 2a-2c too often, because the reference value will then always fluctuate a little.<\/p>\n I applied a supply voltage (AVDD\/AVSS) of about 5 volts and checked the voltage with my multimeter and via In many applications, such as Wheatstone bridges or resistance thermometers, one is not interested in absolute voltage values, but rather in resistances determined via voltage ratios<\/em> and reference resistances. By applying a current across the sought resistor and across the reference resistor, and using the voltage drop across the reference resistor as the reference voltage, the sought resistor can be determined independently of current variations. This will be the subject of my next post.<\/p>\n\n The voltage to be converted can be amplified with the PGA (Programmable Gain Amplifier). Gain factors between 1 and 128 are available. As described earlier, you leave the linear range when the output voltage of the PGA approaches AVDD or AVSS to less than 200 millivolts. You can bypass this restriction by bypassing the PGA. Confusingly, you can still apply gains of 1, 2 or 4.<\/p>\n These are the functions:<\/p>\n There are still a few things to keep in mind:<\/strong><\/p>\n To illustrate how the PGA state and gain changes, I wrote the following sketch. As you can see, forced changes are made to the settings under certain conditions, but they are also undone when the conditions are changed back.<\/p>\n<\/p>\n \u00a0<\/p>\n<\/div>\n \n\n Here is the output:<\/p>\n The ADS1220 allows you to set up constant currents between 10 microamps and 1.5 milliamps on two pins. These currents are referred to as IDAC1 and IDAC2. Since the current is known and the ADS1220 measures the voltage needed to generate the current, you can conveniently measure resistances this way. A typical application is temperature measurement with resistance thermometers.<\/p>\n I would like to demonstrate the function with a simple example. To do this, place a 10 k\u03a9 resistor between AIN0 and AIN1 or between AIN2 and AIN1, respectively. Connect AIN1 to AVSS.<\/p>\n Then upload the following sketch:<\/p>\n<\/p>\n \u00a0<\/p>\n<\/div>\n \n\n Your output should look like this or similar:<\/p>\n\n The handling of IDACs is simple:<\/p>\n Then you simply measure the voltage at the current output pin and calculate the resistance. As you can see, you can also merge IDAC1 and IDAC2.<\/p>\n You have to take care that the current is only high enough for the ADS1220 to generate the necessary voltage. According to the data sheet, the IDAC voltage should not exceed AVDD minus 0.9 volts.<\/p>\n The IDACs have a typical deviation of one percent. So, this is not a precision measurement. It is better to use reference resistors (see next article).<\/p>\n\n The other settings of the ADS1220 have fewer “side effects”. I have therefore summarized them in a sketch and also included the functions already covered once again. This should be quite a convenient template for your own sketches. You just have to uncomment the corresponding functions and apply your parameters. The sketch is called ADS1220_WE_all_settings.ino and is, like the previous examples, part of the library.<\/p>\n\n Here is the sketch:<\/p>\n<\/p>\n \u00a0<\/p>\n<\/div>\n \n\n You select the operating mode with The ADS1220 works according to the oversampling principle. In simple terms, the voltages are converted in high frequency (modulator frequency) and the result is averaged. The more measurements there are, the lower the noise.<\/p>\n The default setting is “Normal Mode”. The modulator frequency in normal mode is one 16th of the frequency of the ADS1220. When using the internal 4.096 MHz oscillator, the modulator frequency is 256 kHz accordingly.<\/p>\n In duty cycle mode, the ADS1220 operates as in normal mode, but with a duty cycle of 25%. The remaining 75% of the time, the ADS1220 is in power down mode. This saves considerable power, but increases the noise. At a data rate of x in duty cycle mode, the noise is comparable to the noise at a data rate of 4x in normal mode.<\/p>\n In Turbo Mode the modulator frequency is doubled. As a result, more transformations are performed in the same time. Accordingly, the noise decreases compared to Normal Mode, as long as you apply comparable data rates. You can also achieve the highest data rates in Turbo Mode.<\/p>\n\n You can set the data rate with The maximum data rate is 2000 SPS. I verified this by determining the time required for 2000 measurements in continuous mode. The result was 1031 milliseconds, which is only a bit slower than theoretically expected. I chose the continuous mode because in this mode the time needed to request the next reading is irrelevant. In single-shot mode, the time for 2000 measurements was 1327 milliseconds.<\/p>\n In general, the higher the data rate, the lower the oversampling and correspondingly higher the noise. The data sheet contains a series of tables listing the noise level depending on the settings. I find the information in ENOB (=effective number of bits), i.e. the actual noise-free bits, particularly informative. At the slowest data rate in normal mode, the resolution is approx. 20 bits.<\/p>\n\n You can set the conversion mode with In general, the single-shot mode is preferable, as it is saves power. This is because the ADS1220 goes into power down mode after the respective measurement. <\/p>\n In both modes, the microcontroller waits after the request until the measured value is available. In a future version of the library, I will add an interrupt-based approach.<\/p>\n\n You can apply a 50 Hz filter, a 60 Hz filter, or both filters at the same time. The function is By default, the DRDY pin goes LOW when a measured value is ready. Additionally, the DOUT pin (=MISO) can be configured to go LOW as well. The function for this is called However, in DOUT_DRDY mode, it should be noted that, unlike the DRDY pin, the DOUT pin is only active when the CS pin is set to LOW. By default, the program waits for the DRDY pin or the DOUT pin to go LOW before setting the CS pin to LOW to query the measured value. There are two ways to resolve this problem: <\/p>\n If you are using a bipolar power supply and want to cover a symmetrical voltage range for your measurements, you will need to carry out differential measurements. Here is an example circuit:<\/p>\n\n For this circuit, the parameter The ADS1220 is a high-performance ADC with high resolution, high gain, high data rate, low noise and low power consumption. However, to get the most out of the ADS1220 and avoid nonsensical measurements, you need to delve deeper into its technical details than you would with, for example, the 16-bit A\/D converter ADS1115<\/a>. <\/p>\n The ADS1220 really shines in applications where small voltage differences need to be measured, such as Wheatstone bridges or thermocouples. I will present these applications in the next article<\/a>.<\/p>\nTechnical data of the ADS1220<\/h2>\n\n
IC vs. module<\/h3>\n\n
![\"ADS1220](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/ADS1220_module.jpg\")
<\/a>Essential data at a glance<\/h3>\n\n
\n
\n
Pinout of the ADS1220 (module)<\/h3>\n\n
\n
\n
Simple measurements <\/h2>\n\n
Basic Circuit<\/h3>\n\n
![\"Example](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/ADS1220_basic_wiring-1024x692.png\")
<\/a>Best pratice circuits<\/h3>\n\n
If you need different voltages for DGND\/DVDD and AGND\/AVDD<\/h4>\n\n
![\"0](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/08\/ADS1220_resistors-1024x493.png\")
<\/a>A few notes beforehand<\/h3>\n\n
bypassPGA(true)<\/code>.<\/p>\n\n![\"\[](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/ql-cache\/quicklatex.com-299bee013ad4fc930ddb01171aa0c5fd_l3.png\" "\\"Rendered")
<\/p><\/p>\n\nThe sketch<\/h3>\n\n
#include <ADS1220_WE.h>\n#include <SPI.h>\n\n#define ADS1220_CS_PIN 7 \/\/ chip select pin\n#define ADS1220_DRDY_PIN 6 \/\/ data ready pin \n\n\/* Create your ADS1220 object *\/\nADS1220_WE ads = ADS1220_WE(ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\/* Alternatively you can also pass the SPI object as reference *\/\n\/\/ ADS1220_WE ads = ADS1220_WE(&SPI, ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\nvoid setup(){\n Serial.begin(9600);\n if(!ads.init()){\n Serial.println(\"ADS1220 is not connected!\");\n while(1);\n }\n\/* The voltages to be measured need to be between negative VREF + 0.2 V and positive\n * VREF -0.2 V if PGA is enabled. For this basic example I disable PGA, to be on the \n * safe side.\n *\/\n ads.bypassPGA(true); \n}\n\n\/* \n * You set the channels to be measured with setCompareChannels(); You\n * can choose the following parameters:\n * Parameter Pos. Input Neg. Input Comment\n * ADS1220_MUX_0_1 AIN0 AIN1\n * ADS1220_MUX_0_2 AIN0 AIN2\n * ADS1220_MUX_0_3 AIN0 AIN3\n * ADS1220_MUX_1_2 AIN1 AIN2\n * ADS1220_MUX_1_3 AIN1 AIN3\n * ADS1220_MUX_2_3 AIN2 AIN3\n * ADS1220_MUX_1_0 AIN1 AIN0\n * ADS1220_MUX_3_2 AIN3 AIN2\n * ADS1220_MUX_0_AVSS AIN0 AVSS single-ended\n * ADS1220_MUX_1_AVSS AIN1 AVSS single-ended \n * ADS1220_MUX_2_AVSS AIN2 AVSS single-ended\n * ADS1220_MUX_3_AVSS AIN3 AVSS single-ended\n * ADS1220_MUX_REFPX_REFNX_4 REFP0\/REFP1 REFN0\/REFN1 (REFPX-REFNX)\/4; PGA bypassed\n * ADS1220_MUX_AVDD_M_AVSS_4 AVDD AVSS (AVDD-AVSS)\/4; PGA bypassed\n * ADS1220_MUX_AVDD_P_AVSS_2 (AVDD+AVSS)\/2 (AVDD+AVSS)\/2 for self tests\n * \n * The last three modes use the internal reference (2.048 V) and gain = 1, independent of \n * your settings.\n *\/\n\n\nvoid loop(){\n float result = 0.0;\n long longResult = 0;\n \n ads.setCompareChannels(ADS1220_MUX_0_1);\n result = ads.getVoltage_mV();\n longResult = ads.getRawData();\n Serial.print(\"AIN0 vs. AIN1 [mV]: \");\n Serial.println(result);\n Serial.print(\"AIN0 vs. AIN1 (raw): \"); \/\/ raw data\n Serial.println(longResult);\n \n ads.setCompareChannels(ADS1220_MUX_0_AVSS);\n result = ads.getVoltage_mV();\n Serial.print(\"AIN0 vs. AVSS [mV]: \");\n Serial.println(result);\n\n ads.setCompareChannels(ADS1220_MUX_1_AVSS);\n result = ads.getVoltage_mV();\n Serial.print(\"AIN1 vs. AVSS [mV]: \");\n Serial.println(result);\n \n ads.setCompareChannels(ADS1220_MUX_2_AVSS);\n result = ads.getVoltage_muV(); \/\/ request result in microvolts\n Serial.print(\"AIN2 vs. AVSS [\u00b5V]: \");\n Serial.println(result);\n \n ads.setCompareChannels(ADS1220_MUX_3_AVSS);\n result = ads.getVoltage_mV();\n Serial.print(\"AIN3 vs. AVSS [mV]: \");\n Serial.println(result);\n \n ads.setCompareChannels(ADS1220_MUX_AVDD_M_AVSS_4); \/\/ voltage supply \/ 4\n result = ads.getVoltage_mV() * 4.0;\n Serial.print(\"Supply Voltage [mV]: \");\n Serial.println(result);\n\n result = ads.getVRef_V(); \/\/ get the reference voltage\n Serial.print(\"Reference [V]: \");\n Serial.println(result,3); \n \n Serial.print(\"Temperature [\u00b0C]: \"); \/\/ get the temperature\n result = ads.getTemperature();\n Serial.println(result);\n \n Serial.println();\n \n delay(2000);\n}<\/pre>\nExplanations to the sketch<\/h3>\n\n
\n
init()<\/code> you initialize the ADS1220. Among other things, the function performs a reset.<\/li>\nsetCompareChannels()<\/code> defines which inputs are used for the measurement. <\/li>\nADS1220_MUX_REFPX_REFNX_4<\/code> causes the reference voltage REFP0\/REFN0 or REFP1\/REFN1 to be measured. Regardless of your settings, this bypasses the PGA, the gain is 1, and the internal reference is used. To ensure that this also works with reference voltages greater than 2.048 volts, the voltage is reduced to a quarter before the measurement. <\/li>\nADS1220_MUX_AVDD_M_AVSS_4<\/code> you measure a quarter of the supply voltage.<\/li>\nADS1220_MUX_AVDD_P_AVSS_2<\/code> connects AINN and AINP to (AVDD+AGND)\/2. Ideally, you will get 0 as a result. This allows you to determine offsets. <\/li>\ngetVoltage_mV()<\/code> \/ getVoltage_muV()<\/code> provide the result in millivolts and microvolts. It is always waited until DRDY goes LOW. This ensures that you get a “fresh” result. In single-shot mode, the measurements must be initiated. The getVoltage functions take care of that as well.<\/li>\ngetRawData()<\/code>.<\/li>\ngetVRef_V()<\/code> you get the reference voltage in volts. This is not the result of a measurement, but the function returns what you have set. The default setting is 2.048 volts.<\/li>\ngetTemperature()<\/code> provides the temperature in degrees Celsius.<\/li>\n<\/ul>\n\nOutput<\/h3>\n\n
![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/output__ADS1220_basic_example.png\")
<\/a>Change of the reference voltage of the ADS1220<\/h2>\n\n
\n
![\"Circuit](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/ADS1220_vref_wiring-1024x670.png\")
<\/a>An example sketch<\/h3>\n\n
#include <ADS1220_WE.h>\n#include <SPI.h>\n\n#define ADS1220_CS_PIN 7 \/\/ chip select pin\n#define ADS1220_DRDY_PIN 6 \/\/ data ready pin \n\n\/* Create your ADS1220 object *\/\nADS1220_WE ads = ADS1220_WE(ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\/* Alternatively you can also pass the SPI object as reference *\/\n\/\/ ADS1220_WE ads = ADS1220_WE(&SPI, ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\nvoid setup(){\n Serial.begin(9600);\n if(!ads.init()){\n Serial.println(\"ADS1220 is not connected!\");\n while(1);\n }\n}\n\n\/* For better readability of the code the setting options are explained here and not\n * in loop() where the functions are used.\n * \n * You set the channels to be measured with setCompareChannels(); You\n * can choose the following parameters:\n * Parameter Pos. Input Neg. Input Comment\n * ADS1220_MUX_0_1 AIN0 AIN1\n * ADS1220_MUX_0_2 AIN0 AIN2\n * ADS1220_MUX_0_3 AIN0 AIN3\n * ADS1220_MUX_1_2 AIN1 AIN2\n * ADS1220_MUX_1_3 AIN1 AIN3\n * ADS1220_MUX_2_3 AIN2 AIN3\n * ADS1220_MUX_1_0 AIN1 AIN0\n * ADS1220_MUX_3_2 AIN3 AIN2\n * ADS1220_MUX_0_AVSS AIN0 AVSS (=AGND) single-ended\n * ADS1220_MUX_1_AVSS AIN1 AVSS single-ended \n * ADS1220_MUX_2_AVSS AIN2 AVSS single-ended\n * ADS1220_MUX_3_AVSS AIN3 AVSS single-ended\n * ADS1220_MUX_REFPX_REFNX_4 REFP0\/REFP1 REFN0\/REFN1 (REFPX-REFNX)\/4; PGA bypassed\n * ADS1220_MUX_AVDD_M_AVSS_4 AVDD AVSS (AVDD-AVSS)\/4; PGA bypassed\n * ADS1220_MUX_AVDD_P_AVSS_2 (AVDD+AVSS)\/2 (AVDD+AVSS)\/2 for self tests\n * The last three modes use the internal reference (2.048 V) and gain = 1, independent of \n * your settings.\n * \n * setVRefSource() sets the the reference voltage source. Parameters are:\n * ADS1220_VREF_INT int. reference 2.048 V (default)\n * ADS1220_VREF_REFP0_REFN0 ext. reference = Vrefp0 - Vrefn0\n * ADS1220_VREF_REFP1_REFN1 ext. reference = Vrefp1 - Vrefn1 (REFP1=AIN0, REFN1=AIN3)\n * ADS1220_VREF_AVDD_AVSS ext. reference = supply voltage\n * \n * If you use the above options you also have to set the value of vRef \"manually\":\n * setVRefValue_V(vRef in volts);\n * \n * Alternatively, you can set the reference voltage source and let the ADS1220 measure \n * the reference. Be aware that this is not a measurement with highest precision. \"Calibration\" \n * might be a bit misleading. You should take the lowest data rate (default) for most accurate \n * results. You can use the following functions:\n * setRefp0Refn0AsVrefAndCalibrate();\n * setRefp1Refn1AsVrefAndCalibrate();\n * setAvddAvssAsVrefAndCalibrate();\n * setIntVRef();\n * The latter function sets the default settings. \n *\/\n\nvoid loop(){\n float result = 0.0;\n \n Serial.println(\"1. Standard internal voltage reference\");\n result = ads.getVRef_V(); \/\/ get the reference voltage \n Serial.print(\"Reference, default [V]: \");\n Serial.println(result,3); \n \n Serial.println(\"2. REFP0\/REFN0 as voltage reference, vRef manually set\");\n ads.setVRefSource(ADS1220_VREF_REFP0_REFN0);\n ads.setVRefValue_V(3.295); \/\/ set reference voltage in volts\n result = ads.getVRef_V();\n Serial.print(\"Reference, manually set [V]: \");\n Serial.println(result,3); \n\n Serial.println(\"3. REFP0\/REFN0 as voltage reference, vRef measured by ADS1220\");\n ads.setRefp0Refn0AsVrefAndCalibrate();\n result = ads.getVRef_V();\n Serial.print(\"Reference, measured [V]: \");\n Serial.println(result,3); \n\n Serial.println(\"4. REFP1\/REFN1 as voltage reference, vRef measured by ADS1220\");\n ads.setRefp1Refn1AsVrefAndCalibrate();\n result = ads.getVRef_V();\n Serial.print(\"Reference, measured [V]: \");\n Serial.println(result,3);\n \n Serial.println(\"5. AVDD\/AVSS as voltage reference, vRef measured by ADS1220\");\n ads.setAvddAvssAsVrefAndCalibrate();\n result = ads.getVRef_V();\n Serial.print(\"Reference, measured [V]: \");\n Serial.println(result,3); \n \n Serial.println(\"With 5. you can measure up to AVDD, just try.\");\n ads.setCompareChannels(ADS1220_MUX_2_AVSS);\n result = ads.getVoltage_mV();\n Serial.print(\"AIN2 vs. AVSS [mV]: \");\n Serial.println(result);\n\n ads.setIntVRef(); \/\/ switch back to standard vRef\n Serial.println();\n \n delay(2000);\n}<\/pre>\nThe output<\/h3>\n\n
![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/output_ADS1220_set_voltage_references.png\")
<\/a>Explanations to the sketch<\/h3>\n\n
\n
setVRefSource()<\/code> and specify its value with setVRefValue()<\/code>.<\/li>\n\n
setRefp0Refn0AsVrefAndCalibrate()<\/code>: REFP0\/REFN0<\/li>\nsetRefp1Refn1AsVrefAndCalibrate()<\/code>: REFP1\/REFN1<\/li>\nsetAvddAvssAsVrefAndCalibrate():<\/code> AVDD\/AVSS<\/li>\n<\/ol>\n<\/li>\n<\/ol>\nsetAvddAvssAsVrefAndCalibrate()<\/code> and getVRef_V()<\/code>. The deviation was a maximum of one millivolt.<\/p>\n\nWhat’s the point of all these references?<\/h3>\n\n
Setting PGA and Gain<\/h2>\n\n
\n
setGain()<\/code>: sets the gain factor (1, 2, 4, 8, 16, 32, 64 or 128).<\/li>\ngetGainFactor()<\/code>: returns the actual gain factor as a byte value. The actual gain factor may differ from the value you set before (see below).<\/li>\nbypassPGA(true\/false)<\/code>: bypasses the PGA or switches it on again.<\/li>\nisPGABypassed():<\/code> returns true if the PGA is bypassed, false otherwise. Again, the value may differ from your preset.<\/li>\n<\/ul>\n\n
bypassPGA()<\/code>.<\/li>\nExample sketch<\/h3>\n\n
#include <ADS1220_WE.h>\n#include <SPI.h>\n\n#define ADS1220_CS_PIN 7\n#define ADS1220_DRDY_PIN 6\n\nADS1220_WE ads = ADS1220_WE(ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\nvoid setup(){\n Serial.begin(9600);\n ads.init();\n ads.setGain(ADS1220_GAIN_8); \/\/ set gain to 8\n ads.bypassPGA(false); \/\/ redundant, since this is default, but I wanted to highlight this setting. \n}\n\nvoid loop(){\n ads.setCompareChannels(ADS1220_MUX_0_1);\n float result = ads.getVoltage_mV();\n byte gain = ads.getGainFactor(); \/\/ queries the (effective) gain\n Serial.print(\"AIN0\/AIN1 [mV]: \");\n Serial.println(result);\n Serial.print(\"PGA bypassed (0: no, 1: yes): \"); \n Serial.println(ads.isPGABypassed()); \/\/ queries if PGA is bypassed, here the result will be 0\n Serial.print(\"Current gain: \"); \/\/ \n \n Serial.println(gain);\n Serial.println();\n \n ads.setCompareChannels(ADS1220_MUX_2_AVSS);\n result = ads.getVoltage_mV();\n gain = ads.getGainFactor();\n Serial.print(\"AIN2\/AVSS [mV]: \");\n Serial.println(result);\n Serial.print(\"PGA bypassed (0: no, 1: yes): \"); \/\/ the PGA will be bypassed\n Serial.println(ads.isPGABypassed());\n Serial.print(\"Current gain: \"); \/\/ gain will be reduced to 4. \n Serial.println(gain);\n Serial.println();\n\n ads.setCompareChannels(ADS1220_MUX_AVDD_M_AVSS_4);\n result = ads.getVoltage_mV();\n gain = ads.getGainFactor();\n Serial.print(\"AVDD\/AVSS [mV]: \");\n Serial.println(result*4.0);\n Serial.print(\"PGA bypassed (0: no, 1: yes): \"); \/\/ the PGA will be bypassed\n Serial.println(ads.isPGABypassed());\n Serial.print(\"Current gain: \"); \/\/ gain will be reduced to 1. \n Serial.println(gain);\n Serial.println();\n \n delay(2000);\n}<\/pre>\n![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/07\/output_ADS1220_pga__settings.png\")
<\/a>IDAC settings<\/h2>\n\n
![\"ADS1220](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/IDAC_test-1024x489.png\")
<\/a>#include <ADS1220_WE.h>\n#include <SPI.h>\n\n#define ADS1220_CS_PIN 7 \/\/ chip select pin\n#define ADS1220_DRDY_PIN 6 \/\/ data ready pin \n\nADS1220_WE ads = ADS1220_WE(ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\nvoid setup() {\n Serial.begin(9600);\n if (!ads.init()) {\n Serial.println(\"ADS1220 is not connected!\");\n while (1);\n }\n \/\/ ads.setCompareChannels(ADS1220_MUX_0_1); default seeting for this test\n ads.setGain(ADS1220_GAIN_1);\n ads.bypassPGA(true); \/\/ since the negative voltage is AVSS, we have to bypass PGA \n\n \/* The ADS1220 can provide two excitation currents, IDAC1 and IDAC2. It takes up to 200\u00b5s\n until the current is set up. The library includes a delay, so you don't have to add one.\n You can switch IDAC1 and IDAC2 on and off individually but the current is the same for \n both.\n The ADS1220 will try to provide the voltage needed for the current you have chosen. This \n voltage shall not exceed AVDD - 0.9V.\n\n ADS1220_IDAC_OFF \/\/ default\n ADS1220_IDAC_10_MU_A \/\/ set IDAC1\/IDAC2 to 10 \u00b5A\n ADS1220_IDAC_50_MU_A \/\/ 50 \u00b5A\n ADS1220_IDAC_100_MU_A \/\/ 100 \u00b5A\n ADS1220_IDAC_250_MU_A \/\/ 250 \u00b5A\n ADS1220_IDAC_500_MU_A \/\/ 500 \u00b5A\n ADS1220_IDAC_1000_MU_A \/\/ 1000 \u00b5A\n ADS1220_IDAC_1500_MU_A \/\/ 1500 \u00b5A\n *\/\n ads.setIdacCurrent(ADS1220_IDAC_100_MU_A);\n\n \/* You can choose to which pin IDAC1 and IDAC2 are directed. The parameters are self-explaining.\n ADS1220_IDAC_NONE\n ADS1220_IDAC_AIN0_REFP1\n ADS1220_IDAC_AIN1\n ADS1220_IDAC_AIN2\n ADS1220_IDAC_AIN3_REFN1\n ADS1220_IDAC_REFP0\n ADS1220_IDAC_REFN0\n *\/\n \/\/ ads.setIdac1Routing(ADS1220_IDAC_AIN0_REFP1);\n \/\/ ads.setIdac2Routing(ADS1220_IDAC_AIN2);\n\n} \/\/ end of setup()\n\nvoid loop() {\n float result = 0.0;\n\n ads.setIdac1Routing(ADS1220_IDAC_AIN0_REFP1);\n result = ads.getVoltage_mV(); \n Serial.print(\"Voltage, caused by IDAC1 [mV]: \");\n Serial.println(result, 3); \/\/ will be roughly 1000 mA, according to Ohm's law\n\n ads.setIdac2Routing(ADS1220_IDAC_AIN2);\n result = ads.getVoltage_mV(); \n Serial.print(\"Voltage, caused by IDAC1 and IDAC2 [mV]: \");\n Serial.println(result, 3); \/\/ will be roughly 2000 mA, according to Ohm's law\n\n ads.setIdac1Routing(ADS1220_IDAC_NONE);\n ads.setIdac2Routing(ADS1220_IDAC_NONE);\n Serial.println();\n \n delay(2000);\n}<\/pre>\nOutput<\/h3>\n\n
![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2022\/06\/output_ads1220_idac_test.png\")
<\/a>Explanations<\/h3>\n\n
\n
setIdacCurrent(ADS1220_IDAC_100_MU_A);<\/code> sets the current to the desired value, here it is 100 microamps. IDAC1 and IDAC2 are identical in terms of current level.<\/li>\nsetIdac1Routing(ADS1220_IDAC_AIN0_REFP1);<\/code> sets pin AIN0\/REFP1 as current source for IDAC1. For IDAC2 you proceed accordingly, if you want to apply two currents. Use the parameter ADS1220_IDAC_NONE<\/code> to turn off the power.<\/li>\n<\/ul>\nOther settings of the ADS1220<\/h2>\n\n
The sketch<\/h3>\n\n
#include <ADS1220_WE.h>\n#include <SPI.h>\n\n#define ADS1220_CS_PIN 7 \/\/ chip select pin\n#define ADS1220_DRDY_PIN 6 \/\/ data ready pin \n\n\/* Create your ADS1220 object *\/\nADS1220_WE ads = ADS1220_WE(ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\/* Alternatively you can also pass the SPI object as reference *\/\n\/\/ ADS1220_WE ads = ADS1220_WE(&SPI, ADS1220_CS_PIN, ADS1220_DRDY_PIN);\n\nvoid setup() {\n Serial.begin(9600);\n if (!ads.init()) {\n Serial.println(\"ADS1220 is not connected!\");\n while (1);\n }\n\n \/* General settings \/ commands *\/\n \/\/ ads.start(); \/\/ wake up from power down and start measurement\n \/\/ ads.reset(); \/\/ resets the ADS1220; all settings will change to default\n \/\/ ads.powerDown(); \/\/ send the ADS1220 to sleep\n \/\/ ads.setSPIClockSpeed(8000000); \/\/ set SPI clock speed, default is 4 MHz\n\n \/* You set the channels to be measured with setCompareChannels(); You\n can choose the following parameters:\n Parameter Pos. Input Neg. Input Comment\n ADS1220_MUX_0_1 AIN0 AIN1 default\n ADS1220_MUX_0_2 AIN0 AIN2\n ADS1220_MUX_0_3 AIN0 AIN3\n ADS1220_MUX_1_2 AIN1 AIN2\n ADS1220_MUX_1_3 AIN1 AIN3\n ADS1220_MUX_2_3 AIN2 AIN2\n ADS1220_MUX_1_0 AIN1 AIN0\n ADS1220_MUX_3_2 AIN3 AIN2\n ADS1220_MUX_0_AVSS AIN0 AVSS (=AGND) single-ended\n ADS1220_MUX_1_AVSS AIN1 AVSS single-ended\n ADS1220_MUX_2_AVSS AIN2 AVSS single-ended\n ADS1220_MUX_3_AVSS AIN3 AVSS single-ended\n ADS1220_MUX_REFPX_REFNX_4 REFP0\/REFP1 REFN0\/REFN1 (REFPX-REFNX)\/4; PGA bypassed\n ADS1220_MUX_AVDD_M_AVSS_4 AVDD AVSS (AVDD-AVSS)\/4; PGA bypassed\n ADS1220_MUX_AVDD_P_AVSS_2 (AVDD+AVSS)\/2 (AVDD+AVSS)\/2 for self tests\n The last three modes use the internal reference (2.048 V) and gain = 1, independent of\n your settings.\n *\/\n \/\/ ads.setCompareChannels(ADS1220_MUX_0_3);\n\n \/* You can choose a gain between 1 (default) and 128 using setGain() if PGA is enabled\n (default). If PGA is disabled you can still choose a gain factor up to 4. If PGA is\n enabled, the amplified voltage shall be between AVSS + 200mV and AVDD - 200mV. Outside\n this range linearity drops. For details check the data sheet, section 8.3.2.1.\n\n If you apply a single-ended mode (negative AINx = AVSS), PGA must be bypassed. Accordingly,\n the maximum gain is 4. The library does these settings automatically.\n\n For the measurement of reference voltages \/ supply voltage PGA will also be bypassed. In\n this case gain is 1.\n\n The parameters you can choose for setGain() are:\n ADS1220_GAIN_X with X = 1,2,4,8,16,32,64 or 128\n\n With getGainFactor() you can query the gain. The function returns the effective gain and\n not the gain set in the register. Under certian conditions thes are are different. For\n example, the effective gain is set to 1 when external references are measured.\n *\/\n ads.setGain(ADS1220_GAIN_1);\n \/\/ ads.getGainFactor(); \/\/ returns the effective gain as a byte value\n \/\/ ads.bypassPGA(true); \/\/ true disables PGA, false enables PGA\n \/\/ ads.isPGABypassed(); \/\/ returns true, if PGA is bypassed\n\n \/* The data rate level with setDataRate(). The data rate itself also depends on the operating\n mode and the clock. If the internal clock is used or an external clock with 4.096 MHz the data\n rates are as follows (per second):\n\n Level Normal Mode Duty-Cycle Turbo Mode\n ADS1220_DR_LVL_0 20 5 40 (default)\n ADS1220_DR_LVL_1 45 11.25 90\n ADS1220_DR_LVL_2 90 22.5 180\n ADS1220_DR_LVL_3 175 44 350\n ADS1220_DR_LVL_4 330 82.5 660\n ADS1220_DR_LVL_5 600 150 1200\n ADS1220_DR_LVL_6 1000 250 2000\n\n The higher the data rate, the higher the noise (tables are provided in section 7.1 in the\n data sheet). In single-shot mode the conversion times equal the times in Normal Mode.\n *\/\n \/\/ ads.setDataRate(ADS1220_DR_LVL_2);\n\n \/* Using setOperatingMode() you choose the operating mode. Possible parameters are:\n ADS1220_NORMAL_MODE -> Normal Mode\n ADS1220_DUTY_CYCLE_MODE -> Duty cycle mode. Saves power, but noise is higher.\n ADS1220_TURBO_MODE -> Turbo Mode for fast measurements\n *\/\n \/\/ ads.setOperatingMode(ADS1220_DUTY_CYCLE_MODE);\n\n \/* You can choose between a continuous and a single-shot (on demand) mode with\n setConversionMode(). Parameters are:\n ADS1220_SINGLE_SHOT (default)\n ADS1220_CONTINUOUS\n *\/\n \/\/ ads.setConversionMode(ADS1220_CONTINUOUS);\n\n \/* In order to obtain temperature values, choose enableTemperatureSensor(true); false will\n disable the temperature sensor. As long as the temperature sensor is enabled the ADS1220\n is blocked for this task. To obtain voltage values, you have to switch the sensor off. The\n temperature is queried with getTemperature();\n *\/\n \/\/ ads.enableTemperatureSensor(true);\n \/\/ ads.getTemperature(); \/\/ returns temperature as float\n\n \/*\n setVRefSource() sets the the reference voltage source. Parameters are:\n ADS1220_VREF_INT int. reference 2.048 V (default)\n ADS1220_VREF_REFP0_REFN0 ext. reference = Vrefp0 - Vrefn0\n ADS1220_VREF_REFP1_REFN1 ext. reference = Vrefp1 - Vrefn1 (REFP1=AIN0, REFN1=AIN3)\n ADS1220_VREF_AVDD_AVSS ext. reference = supply voltage\n\n If you use the above options you also have to set the value of vRef \"manually\":\n setVRefValue_V(vRef in volts);\n\n Alternatively, you can set the reference voltage source and let the ADS1220 measure\n the reference. Be aware that this is not a measurement with highest precision.\n \"Calibration\" might be a bit misleading. You should take the lowest data rate (default)\n for most accurate results. You can use the following functions:\n setRefp0Refn0AsVrefAndCalibrate();\n setRefp1Refn1AsVrefAndCalibrate();\n setAvddAvssAsVrefAndCalibrate();\n setIntVRef();\n The latter function sets the default settings.\n\n Be aware that VREFPx must be >= VREFNx + 0.75V.\n *\/\n \/\/ ads.setVRefSource(ADS1220_VREF_REFP0_REFN0);\n \/\/ ads.setVRefValue_V(3.312); \/\/ just an example\n \/\/ or:\n \/\/ ads.setRefp0Refn0AsVrefAndCalibrate(); \/\/or:\n \/\/ ads.setRefp1Refn1AsVrefAndCalibrate(); \/\/or:\n \/\/ ads.setAvddAvssAsVrefAndCalibrate(); \/\/or:\n \/\/ ads.setIntVRef();\n \/\/ to query VRef:\n \/\/ ads.getVRef_V(); \/\/ returns VRef as float\n\n \/* You can set a filter to reduce 50 and or 60 Hz noise with setFIRFilter(); Parameters:\n ADS1220_NONE no filter (default)\n ADS1220_50HZ_60HZ 50Hz and 60Hz filter\n ADS1220_50HZ 50Hz filter\n ADS1220_60HZ 60Hz filter\n *\/\n \/\/ ads.setFIRFilter(ADS1220_50HZ_60HZ);\n\n \/* When data is ready the DRDY pin will turn from HIGH to LOW. In addition, also the DOUT pin\n can be set as a data ready pin. The function is setDrdyMode(), parameters are:\n ADS1220_DRDY only DRDY pin is indicating data readiness (default);\n ADS1220_DOUT_DRDY DRDY and DOUT pin indicate data readiness\n *\/\n \/\/ ads.setDrdyMode(ADS1220_DOUT_DRDY);\n\n\n \/* There is a switch between AIN3\/REFN1 and AVSS. You can use this option to save power in\n bridge sensor applications.\n ADS1220_ALWAYS_OPEN The switch is always open.\n ADS1220_SWITCH Switch automatically closes when the START\/SYNC command is sent\n and opens when the POWERDOWN command is issued.\n *\/\n \/\/ ads.setLowSidePowerSwitch(ADS1220_SWITCH);\n\n \/* The ADS1220 can provide two excitation currents, IDAC1 and IDAC2. It takes up to 200\u00b5s\n until the current is set up. The library includes a delay, so you don't have to add one.\n You can switch IDAC1 and IDAC2 on and off individually but the current is the same for \n both.\n The ADS1220 will try to provide the voltage needed for the current you have chosen. This \n voltage shall not exceed AVDD - 0.9V.\n\n ADS1220_IDAC_OFF \/\/ default\n ADS1220_IDAC_10_MU_A \/\/ set IDAC1\/IDAC2 to 10 \u00b5A\n ADS1220_IDAC_50_MU_A \/\/ 50 \u00b5A\n ADS1220_IDAC_100_MU_A \/\/ 100 \u00b5A\n ADS1220_IDAC_250_MU_A \/\/ 250 \u00b5A\n ADS1220_IDAC_500_MU_A \/\/ 500 \u00b5A\n ADS1220_IDAC_1000_MU_A \/\/ 1000 \u00b5A\n ADS1220_IDAC_1500_MU_A \/\/ 1500 \u00b5A\n *\/\n \/\/ ads.setIdacCurrent(ADS1220_IDAC_50_MU_A);\n\n \/* You can choose to which pin IDAC1 and IDAC2 are directed. The parameters are self-explaining.\n ADS1220_IDAC_NONE\n ADS1220_IDAC_AIN0_REFP1\n ADS1220_IDAC_AIN1\n ADS1220_IDAC_AIN2\n ADS1220_IDAC_AIN3_REFN1\n ADS1220_IDAC_REFP0\n ADS1220_IDAC_REFN0\n *\/\n \/\/ ads.setIdac1Routing(ADS1220_IDAC_AIN0_REFP1);\n \/\/ ads.setIdac2Routing(ads1220IdacRouting route);\n\n} \/\/ end of setup()\n\nvoid loop() {\n float result = 0.0;\n\n \/* The following functions query measured values from the ADS1220. If you request values in\n single-shot mode, the conversion will be initiated automatically. The value will be delivered\n once DRDY goes LOW. This ensures that you will receive \"fresh\" data. This is particularly\n important when you change channels.\n *\/\n result = ads.getVoltage_mV(); \/\/ get result in millivolts\n \/\/ ads.getVoltage_muV(); \/\/ get result in microvolts\n \/\/ ads.getRawData(); \/\/ get raw result (signed 24 bit as long int)\n \/\/ ads.getTemperature(); \/\/ get temperature (you need to enable the T-sensor before);\n Serial.println(result, 3);\n \n delay(2000);\n}<\/pre>\nExplanations to the sketch and settings<\/h3>\n\n
General settings \/ functions<\/h4>\n\n
\n
start()<\/code>: wakes up the ADS1220 from power down mode. Moreover, the function starts single or continuous measurements. However, you don’t need it for this purpose, since start()<\/code> is called automatically when you request readings.<\/li>\nreset()<\/code>: performs a reset of the ADS1220.<\/li>\npowerDown()<\/code>: sends the ADS1220 into power down mode. In this state, the current consumption drops to typically 0.1 microampere.<\/li>\nsetSPIClockSpeed()<\/code>: sets the SPI clock frequency. Default setting is 4 MHz.<\/li>\n<\/ul>\n\nSetting the operating mode <\/h4>\n\n
setOperatingMode()<\/code>. The following parameters are available:<\/p>\n\n
Set the data rate<\/h4>\n\n
setDataRate()<\/code>.ADS1220_DR_LVL_x<\/code> The level
with x = 0 to 6 are available as parameters. The actual data rate in PLC depends on the level and the operating mode. You can find a table in the sketch (or in the datasheet).<\/p>\nSetting the conversion mode<\/h4>\n\n
setConversionMode()<\/code>. The two possible parameters are:<\/p>\n\n
ADS1220_SINGLE_SHOT<\/code>: Single-Shot = “On request”<\/li>\nADS1220_CONTINUOUS<\/code>: continuous<\/li>\n<\/ul>\n50 and 60 Hertz filter<\/h4>\n\n
setFIRFilter()<\/code>. FIR stands for “finite impulse response”. You can find the parameters in the sketch above. For more details, please have a look at the datasheet.<\/p>\n\nDRDY settings <\/h4>\n\n
setDrdyMode()<\/code>, the parameters available for selection are:<\/p>\n\n
ADS1220_DRDY<\/code>: only the DRDY pin shows a new measured value.<\/li>\nADS1220_DOUT_DRDY<\/code>DRDY and DOUT show a new measured value.<\/li>\n<\/ul>\n\n
digitalRead()<\/code>. Here, too, DRDY remains unconnected and you pass the MISO pin as the DRDY pin. Of course, this is not an ideal solution. <\/li>\n<\/ol>\n\nMeasurements with bipolar power supply<\/h2>\n\n
![\"Example](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/04\/ADS1220_bipolar_supply_small-1024x404.png\")
<\/a>ADS1220_MUX_0_1<\/code> should be selected for the channels. In this case, you must remove the 0 \u03a9 resistors on the module, if present. <\/p>\n\nThe ADS1220 – conclusion and outlook<\/h2>\n\n