I have already given an overview of the tinyAVR family and its technical features here<\/a>.<\/p>\r\n The data sheets of the tinyAVR microcontrollers have several hundred pages. Of course, I can’t cover all of that in this article. I won’t cover functions that you can also conveniently control via the Arduino language (Wire, SPI, etc.). But I also had to limit myself thematically. So it’s definitely worth taking a look at the data sheet! <\/p>\r\n Here’s what you can expect in this post and its sequels:<\/p>\r\n And one more note in advance: in some sketches, I use I will now try to explain the basic principles of register programming for the tinyAVR series briefly. For detailed information, please refer to the application note TB3262<\/a> from Microchip.<\/p>\r\n\n The following blink sketch for pin PA2 gives a first impression:<\/p>\r\n\n This is very different from coding \u00e0 la The registers are organized in modules. The modules are structures (data type struct), which is why you can see the dot notation in the blink sketch. The name of the structure is the module, the registers are elements of this structure, e.g.<\/p>\r\n To understand bit masks and bit group configuration masks, let’s take a look at the Control A Register (CTRLA) of timer B0 as an example. The module is called TCB. However, as some tinyAVR microcontrollers have two timers B (0 and 1), the number is appended to the module name. In general terms: “MODULNAMEn<\/strong>.REGISTERNAME”. The CTRLA register of timer B0 is therefore called: TCB0.CTRLA. <\/p>\r\n The TCBn.CTRLA registers have various bits and the CLKSEL (Clock Select) bit group:<\/p>\r\n\n Bit masks are used to set single bits. Their names are formed according to the following scheme:<\/p>\r\n The module number is omitted from the bit mask. This is, for example, how you set the ENABLE bit for the timer B0: <\/p>\r\n The bit group configuration masks are used for bit groups (also known as bit fields), the names of which are formed as follows:<\/p>\r\n As an example, we specify that timer B0 uses the TCA clock:<\/p>\r\n CLKTCA corresponds to the CLKSEL value 0x2 or 0b10. In the register, CLKSEL is located at bit position 1 and 2, i.e. it is shifted 1 bit to the left. This is why the value of TCB_CLKSEL_TCA0_gc is 0x4 or 0b100.<\/p>\r\n If you want to mask the bit group TCB_CLKSEL, you can use the bit group mask. Here in the general form:<\/p>\r\n The value of TCB_CLKSEL_gm is 0x6 or 0b110, as you can easily check with Then there are the Bit Positions and the Bit Group Positions:<\/p>\r\n Unsurprisingly, they indicate the position of the bit or bit group in the register. So if you want to determine the current CLKSEL value of timer TCB0, you could do it like this:<\/p>\r\n It may all sound a little complicated at first, but you soon get used to this type of notation. It involves a certain amount of writing, but it pays off because the code is still easy to understand even after a few months.<\/p>\r\n\n This way of programming registers takes some getting used to at first. What helps with orientation is the data sheet of the tinyAVR MCU in question. It is organized according to the modules and for each module there is a “Register Summary” with links to the individual registers, where you can then find the bit masks and bit group masks. <\/p>\r\n\n I also recommend looking at the “I\/O Multiplexing and Considerations” section of the data sheet. There you will find a table showing which pins have which functions. <\/p>\r\n\n Sometimes (but rather rarely) the names for the bitmasks, bitgroups etc. in the data sheet are inconsistent with the names you have to use in the program. Fortunately, the compiler usually provides you with the correct alternative. <\/p>\r\n Otherwise, you will find the definitions in the Arduino installation. Where exactly depends on your installation. For me, the directory is under:<\/p>\r\n C:\\Users\\Ewald\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\avr-gcc\\7.3.0-atmel3.6.1-arduino5\\avr\\include\\avr<\/p>\r\n The files for the ATtinys have the designation iotnxxx<\/em>.h. But even if you don’t have a problem, it is worth taking a look at this.<\/p>\r\n\n As demonstrated by the register summary above, there are a number of registers whose names begin with “DIR” or “OUT”. The “DIR …” registers control which pins are used as INPUT or OUTPUT. With the help of the “OUT …” registers you set the pin level, i.e. HIGH or LOW. The second part of the name means:<\/p>\r\n You can also write directly to the DIR and OUT registers, but the beauty of OUTSET, OUTCLR, OUTTGL and their DIR counterparts is that the instructions are pin-selective. Example:<\/p>\r\n You can use the IN registers to read the status of the pins ( Each pin has its own control register, namely PINxCTRL:<\/p>\r\n\n The INVEN bit allows you to invert the INPUT and OUTPUT values. PULLUPEN activates the internal pull-up resistor. With ISC you can define the interrupt conditions or switch off the digital function of the pin completely (INPUT_DISABLE):<\/p>\r\n\n I’ll come back to the blink sketch and show that there are other ways to achieve the same effect:<\/p>\r\n\n Here is an example of how you can read out individual pins. To do this, connect an LED to PA2 and a push-button, which emits a HIGH signal when pressed, to PA1. As long as you press the button, the LED lights up. <\/p>\r\n\n The following is a simple example of an interrupt on PA1. Apart from the button, which should provide a LOW signal when pressed this time, you use the setup of the last example. Note that the interrupt is not automatically cleared by calling the ISR. You must “manually” clear the bit in the relevant interrupt flag register.<\/p>\r\n\n An interrupt is triggered both when the button is pressed and when it is released. This is only really noticeable if the button is pressed for longer than one second. <\/p>\r\n\n If you use port manipulation \u00e0 la The same code, but with VPORTA.OUT instead of PORTA.OUT required 400 milliseconds. These are not major differences, but they are differences nonetheless.<\/p>\r\n The available VPORTx registers are DIR, OUT, IN and INTFLAGS.<\/p>\r\n\n The registers of the PORTMUX module allow you to assign certain functions to alternative pins. It is best to check the PORTMUX Register Summary to see which functions these are. Here, as an example, is the PORTMUX Register Summary of the ATtiny3224\/6\/7: <\/p>\r\n\n As an example, we redirect the output 1 of timer TCA0. The relevant PORTMUX register is TCAROUTEA. By setting the relevant bit, you change from the default to the alternative:<\/p>\r\n The event system is really cool! It allows certain peripherals, i.e. timers, ADC, USART, etc., to send signals to other peripheral units without involving the CPU. Later in the article, we will have the RTC timer regularly trigger ADC measurements. Normally, you would probably do this via 3 or 6 channels are available for transmitting the event signals. The sender of the signal is called the generator, the receiver is the user. Many users have their own event control register in which further settings can be made. These registers are part of the peripheral modules.<\/p>\r\n\n Generators and users can be synchronous or asynchronous to the system clock. If an asynchronous generator sends an event signal to a synchronous user, the signal must first be synchronized, which takes a few clock cycles. For now, it is only important that you have heard of the distinction. <\/p>\r\n\n In the CHANNELn registers (with n = 0 to 5) you define the generator:<\/p>\r\n\n Most generators can utilise all channels. But there are also exceptions. For example, the pins of port A can only use channels 0 to 3. Here is a small excerpt from the ATtiny3224\/6\/7 data sheet: <\/p>\r\n\n Select a suitable channel and assign the generator to its register (EVSYS.CHANNELn). Compose the generator name according to the following recipe: <\/p>\r\n “EVSYS_” + “CHANNELn_” + Peripheral_ + Output_ + “gc”<\/p>\r\n For example: You define the event users in the USERn registers:<\/p>\r\n\n Here is an excerpt from the table of available event users:<\/p>\r\n\n The complete table(s) can be found in the data sheet in the EVSYS chapter in the register descriptions. The names of the USER registers are composed as follows: <\/p>\r\n “EVSYS.USER” + “Peripheral” + “Input”<\/p>\r\n For example, For a better understanding, let’s take a look at a small example (tested on ATtiny3226). Attach an LED to PA2 and a pushbutton, which pulls the pin LOW when pressed, to PA1. <\/p>\r\n Now we use PA1 as an event generator and EVOUTA (=PA2) as a user. Channels 0 to 3 are available for port A. In the example, we use Channel 0.<\/p>\r\n\n PA2, or EVOUTA, reflects the status of PA1. The LED lights up in the normal state and switches off when the button is pressed. This may not be impressive at first glance, but at second glance it is. We do not query the level of PA1, nor have we set up an external interrupt for it. In addition, there are no instructions for switching the LED in the running program. The processes are all controlled in the background without your running program having to do anything. More useful applications will follow later. <\/p>\r\n\n The event system of tinyAVR series 0 and 1 differs from that of series 2. There are separate registers for the synchronous and asynchronous generators and users. However, the basic principle is the same, which is why I won’t go into detail here. Take a look at the data sheet yourself, search for the EVSYS chapter and perhaps go to the register summary first. This will give you an overview, and you can navigate to the registers from there. <\/p>\r\n\n To help you get started, here is an example sketch for the tinyAVR series 1 and 0. It basically does the same thing as the example for series 2. I tested the sketch on an ATtiny1604 and ATtiny1614.<\/p>\r\n\n In addition to the differences already mentioned, it is noticeable here that the “x” in the EVOUTx is a number and not a letter. It should also be noted that the event output (EVOUTx) must be activated in the PORTMUX.CTRLA register. Finally, it should also be mentioned that the SYNCUSER and ASYCUSER registers are not named by their user, but are numbered consecutively. The numbers can be found in the data sheet in the description of the (A)SYNCUSER registers. <\/p>\r\n\n The RTC module has two features, namely the 16-bit Real-Time Counter (RTC) and the Periodic Interrupt Timer (PIT). Both use the same clock source. Otherwise, the functions can be used independently of each other. The maximum clock rate is 32768 Hz, so you are more likely to control the slower processes with this module.<\/p>\r\n\n Conveniently, the register landscape of the RTC module is almost identical for all tinyAVR representatives. There are differences in the calibration and the selection of clocks.<\/p>\r\n\n The clock is set in the CLKSEL register. The following options are available:<\/p>\r\n A really great feature of the series 2 RTC module is that you can calibrate the underlying clock using the CALIB register.<\/p>\r\n\n ERROR[6:0] is the deviation in ppm. If SIGN is set, the clock is correspondingly faster. In this case, you must set the prescaler to at least DIV2. If SIGN is not set, the clock is slower. <\/p>\r\n\n In the CTRLA register, you specify whether the RTC module should continue to run in standby mode (RUNSTDBY). You also (de)activate the calibration (CORREN, if available) and switch on the module (RTCEN).<\/p>\r\n\n You can use the PRESCALER to slow down the RTC with a maximum factor of 32768:<\/p>\r\n\n A Compare Match and an Overflow Interrupt are available for the RTC. The corresponding Interrupt Flag Register INTFLAG is similar.<\/p>\r\n\n There is only one interrupt vector, namely RTC_CNT_vector, i.e. you have to look in the INTFLAGS register to see which interrupt was triggered.<\/p>\r\n\n The Periodic Interrupt Timer simply does what its name suggests: It triggers an interrupt at regular intervals. In the PITCTRLA register, you can activate the PIT and set the period.<\/p>\r\n\n In PITINTCRTL you activate the PIT interrupt. PITINTFLAGS is similar to PITINTCTRL.<\/p>\r\n\n As a simple example for programming the RTC, a sketch follows, which generates a “slow motion PWM” with a period of 2 seconds and a duty cycle of 75 % at PA2.<\/p>\r\n\n As only one interrupt vector (RTC_CNT_vect) is available for the Overflow and Compare Interrupt, we have to use the interrupt flags to check which event triggered the interrupt.<\/p>\r\n The prescaler is set to 4, i.e. the RTC counts at a frequency of 32768 \/ 4 = 8192 Hz. PER is 16383 and therefore the RTC overflows every 16384 steps, which corresponds to an overflow frequency of 2 seconds. The Compare Value is 12288, i.e. 75% of PER +1.<\/p>\r\n\n The example sketch for the PIT is even simpler. With a period of 16384 and a clock rate of 32768 Hz, an interrupt is triggered every 0.5 seconds. We use it here to toggle PA2.<\/p>\r\n\n However, you can also achieve the same without an interrupt by using PIT as an event generator. The event signal has a duty cycle of 50%. Here is a version for an ATtiny1614: <\/p>\r\n\n The watchdog timer behaves in the same way on all members of the tinyAVR family. I find two features particularly remarkable: <\/p>\r\n The Watchdog Timer (WDT) receives its clock from the ultra low-power oscillator, OSCULP32K.<\/p>\r\n\n You enter the timing parameters for the WDT in control register A, CTRLA.<\/p>\r\n\n You can make the following settings for PERIOD and WINDOW:<\/p>\r\n\n If you only set a value for PERIOD and keep WINDOW at 0, the WDT will run in Normal Mode. If no watchdog reset takes place within the time period defined with PERIOD, a system reset is carried out.<\/p>\r\n If WINDOW is not zero, you are in Window Mode. This is a little more difficult to explain, and perhaps only becomes clear with the example sketch. The following applies in window mode:<\/p>\r\n By setting the LOCK bit, you protect the WDT settings against changes. You can only delete it again in debug mode.<\/p>\r\n If you write data to the CTRLA register, it must be transferred to the WDT clock domain. The SYNCBUSY bit is set during synchronization.<\/p>\r\n\n Normal mode should not require an example sketch. We will therefore only look at one sketch for window mode. The setting for the WDT is: TOWDTW<\/sub> = TOWDT<\/sub> = 4 seconds.<\/p>\r\n\n If you let the sketch run unchanged, the while() loop counts up until TOWDTW<\/sub> + TO If you uncomment lines 15 to 17, there is a If you then change line 15 so that the And what’s the point of all this? The watchdog normally bites if the sketch gets stuck somewhere. You can use the window method to trigger a system reset if an action is executed too early, for example because some other step has not been executed for whatever reason.<\/p>\r\n\n The A\/D converter of the tinyAVR microcontroller would certainly deserve a separate article. However, I will keep this chapter short and once again refer to the data sheets. <\/p>\r\n The ADC modules of tinyAVR series 0 and 1 differ fundamentally from those of series 2.<\/p>\r\n\n\r\n
Serial output<\/h4>\n\n
Serial.print()<\/code>. To get an output on the serial monitor, use a USB-to-TTL adapter and connect RX to TX, TX to RX and GND to GND. Don’t forget to set the port. If you are not uploading the sketches via UPDI, but already using the bootloader and USB-to-TTL adapter, then the serial output will work anyway. <\/p>\r\n\nRegister programming of the tinyAVR series<\/h2>\n\n
Everything is a little different<\/h3>\n\n
void setup() {\r\n PORTA.DIRSET = PIN2_bm; \/\/ set PA2 (selectively!) to OUTPUT\r\n}\r\n \r\nvoid loop() {\r\n PORTA.OUTSET = PIN2_bm; \/\/ set PA2 to HIGH \r\n delay(200);\r\n PORTA.OUTCLR = PIN2_bm; \/\/ set PA2 to LOW\r\n delay(200);\r\n}<\/pre>\r\n\nPORTA |= (1<<PA2)<\/code> that you are probably more familiar with.<\/p>\r\n\nRegister<\/h4>\n\n
\r\n
\r\n
Bit Masks and Bit Group Configuration Masks<\/h4>\n\n
![\"TCBn.CTRLA](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/09\/red_tcb_ctrla-1-1024x281.png\")
<\/a>\r\n
TCB0.CTRLA |= TCB_ENABLE_bm;<\/code><\/p>\r\n\r\n
TCB0.CTRLA |= TCB_CLKSEL_TCA0_gc;<\/code><\/p>\r\n\n\r\n
Serial.println(TCB_CLKSEL_gm, BIN)<\/code>.<\/p>\r\n\nBit Positions and Bit Group Positions<\/h4>\n\n
\r\n
Serial.println( ((TCB0.CTRLA & TCB_CLKSEL_gm) >> TCB_CLKSEL_gp) );<\/code><\/p>\r\n\nOrientation in the Data Sheet <\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/reg_summary_portx-1.webp\")
<\/a>Looking up the definitions<\/h4>\n\n
I\/O Control – PORTx Module<\/h2>\n\n
PORTx Register <\/h3>\n\n
DIR, OUT and IN registers<\/h4>\n\n
\r\n
\r\n
PORTx.OUT = PINy_bm;<\/code> sets pin y (with y = 0 to 7) of port x to HIGH and all other pins of port x to LOW. Here x = A, B or C, depending on which ports are available. <\/li>\r\nPORTx.OUTSET = PINy_bm;<\/code> only acts on pin y, i.e. the statement corresponds to PORTx.OUT |= PINy_bm;<\/code>.<\/li>\r\n<\/ul>\r\ndigitalRead()<\/code>, so to speak). However, if you write a bit to the PORTx.IN register, the corresponding bit is toggled in PORTx.OUT. The IN register is the counterpart to the PINx register of traditional AVR microcontrollers.<\/p>\r\n\nControl Register PINxCTRL <\/h4>\n\n
![\"Arduino](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_PORTx_PINx_CTRL-1024x82.png\")
<\/a>![\"ISC[2:0]](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/PINxCTRL_ISC_table.webp\")
<\/a>Example Sketches for PORTx<\/h3>\n\n
Switching Pins<\/h4>\n\n
void setup() {\r\n PORTA.DIRSET = PIN2_bm; \/\/ set PA2 to OUTPUT\r\n \/\/ PORTA.DIR |= (1<<2);\r\n \/\/ PORTA.DIR |= (1<<PIN2_bp); \/\/ bp = bit position\r\n}\r\n\r\nvoid loop() {\r\n PORTA.OUTSET = PIN2_bm; \/\/ set PE2 to HIGH\r\n \/\/ PORTA.OUT |= PIN2_bm;\r\n delay(200);\r\n PORTA.OUTCLR = PIN2_bm;\r\n \/\/ PORTA.OUT &= ~PIN2_bm; \r\n delay(200);\r\n \r\n \/\/ Alternative: toggle pin:\r\n \/\/ PORTA.OUTTGL = PIN2_bm;\r\n \/\/ delay(200); \r\n}<\/pre>\r\n\nReading Pin Levels <\/h4>\n\n
void setup() {\r\n PORTA.DIRSET = PIN2_bm; \/\/ PA1: OUTPUT\r\n PORTA.DIRCLR = PIN1_bm; \/\/ PA2: INPUT\r\n}\r\n\r\nvoid loop(){\r\n if(PORTA.IN & PIN1_bm){\r\n PORTA.OUTSET = PIN2_bm;\r\n }\r\n else{\r\n PORTA.OUTCLR = PIN2_bm;\r\n }\r\n}<\/pre>\r\n\nSetting up Interrupts<\/h4>\n\n
volatile bool event = false;\r\n\r\nISR(PORTA_PORT_vect){\r\n PORTA.INTFLAGS = PIN1_bm; \/\/ clear interrupt (writing a \"1\" clears the bit!)\r\n event = true;\r\n}\r\n\r\nvoid setup() {\r\n PORTA.DIRSET = PIN2_bm;\r\n PORTA.DIRCLR = PIN1_bm; \/\/ redundant in this case\r\n PORTA.PIN1CTRL = PORT_PULLUPEN_bm | PORT_ISC_BOTHEDGES_gc; \/\/ Pull-Up \/ Interrupt n both edges\r\n}\r\n\r\nvoid loop(){\r\n if(event){\r\n PORTA.OUTSET = PIN2_bm;\r\n delay(1000);\r\n PORTA.OUTCLR = PIN2_bm;\r\n event = false;\r\n }\r\n}<\/pre>\r\n\nVirtual Ports<\/h4>\n\n
PORTA.OUT = (1 << 2);<\/code>, you should use the virtual port registers instead of the “normal” port registers. To do this, simply place a “V” before PORTx, i.e.: VPORTA.OUT = (1 << 2);<\/code>. The virtual ports are copies of the ports in the lower address space. Port manipulations are performed faster when using the virtual ports. The following code took 501 milliseconds to execute on an ATtiny3226 at 20 MHz: <\/p>\r\nfor(unsigned long i=0; i<1000000;i++){\r\n PORTA.OUT = 0;\r\n PORTA.OUT = (1<<2);\r\n}<\/pre>\r\n\nReassigning Inputs \/ Outputs – PORTMUX Module<\/h2>\n\n
![\"\"](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/portmux_reg_sum_322xpng-1.png\")
<\/a>\r\n
PORTMUX.TCAROUTEA |= PORTMUX_TCA01_bm;<\/code><\/li>\r\n<\/ul>\r\n\nThe Event System – EVSYS Module<\/h2>\n\n
delay()<\/code>, millis()<\/code> or timer interrupts. However, all these options have certain disadvantages. <\/p>\r\nEVSYS module of the tinyAVR series 2<\/h3>\n\n
CHANNELn Register – Definition of the Generator <\/h4>\n\n
![\"EVSYS.CHANNELs](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/reg_evnt_channeln_series2-1024x84.png\")
<\/a>![\"Event](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/event_gen_series2-1.png\")
<\/a>EVSYS_CHANNEL0_PORTA_PIN1_gc;<\/code><\/p>\r\n\nRegister USERn – Definition of the users<\/h4>\n\n
![\"Register](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/reg_evsys_user_series2-1024x83.png\")
<\/a>![\"\"](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/event_users_series2.png\")
<\/a>EVSYS.USEREVSYSEVOUTA<\/code>. You assign the channel to the USER register from which it is sent. <\/p>\r\n\nA simple event example<\/h4>\n\n
void setup() {\r\n PORTA.DIRCLR = PIN1_bm; \/\/ PA1 INPUT\r\n PORTC.DIRSET = PIN2_bm; \/\/ PA2 (=EVOUTA) OUTPUT \r\n PORTA.PIN1CTRL |= PORT_PULLUPEN_bm;\r\n \r\n EVSYS.CHANNEL0 = EVSYS_CHANNEL0_PORTA_PIN1_gc; \/\/ PA1 is event generator for channel 0\r\n EVSYS.USEREVSYSEVOUTA = EVSYS_USER_CHANNEL0_gc; \/\/ EVOUTA is user of event channel 0 \r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nEVSYS of the tinyAVR series 0 and 1<\/h3>\n\n
![\"EVSYS](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2024\/10\/evsys_reg_summary_1614_6_7-1024x353.png\")
<\/a>EVSYS example sketch for tinyAVR series 0 and 1<\/h4>\n\n
void setup() {\r\n PORTA.DIRCLR = PIN1_bm; \/\/ PA1 INPUT\r\n PORTA.DIRSET = PIN2_bm; \/\/ PA2 (=EVOUT0) OUTPUT \r\n PORTA.PIN1CTRL |= PORT_PULLUPEN_bm;\r\n \r\n PORTMUX.CTRLA |= PORTMUX_EVOUT0_bm; \/\/ Event output needs to be enabled for tinyAVR 0\/1\r\n EVSYS.ASYNCCH0 = EVSYS_ASYNCCH0_PORTA_PIN1_gc; \/\/ PA1 is async. event generator for channel 0\r\n EVSYS.ASYNCUSER8 = EVSYS_ASYNCUSER8_ASYNCCH0_gc; \/\/ ASYNCUSER8 = EVOUT0 = channel 0 user \r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nReal-Time Counter – RTC Module<\/h2>\n\n
The registers of the RTC module<\/h3>\n\n
Clock Selection Register CLKSEL<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_CLKSEL-1024x82.webp\")
<\/a>\r\n
\r\n
Crystal Frequency Calibration Register CALIB (tinyAVR Series 2 only)<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_CALIB-1024x90.webp\")
<\/a>RTC Control Register A CTRLA<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_CTRLA-1024x87.webp\")
<\/a>![\"PRESCALER[3:0]](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_DIV_table-1024x381.webp\")
<\/a>RTC Interrupt Control Register INTCTRL<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_INTCTRL-1024x85.webp\")
<\/a>PIT Control Register A CTRLA<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_PITCTRLA-1024x89.webp\")
<\/a>![\"PERIOD[3:0]](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_CYCLE_table.webp\")
<\/a>PIT Interrupt Control Register PITINTCTRL<\/h4>\n\n
![\"RTC.PITINTCTRL](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_RTC_PITINTCTRL-1024x81.webp\")
<\/a>Example Sketches for RTC and PIT<\/h3>\n\n
RTC example sketch<\/h4>\n\n
ISR(RTC_CNT_vect){\r\n if(RTC.INTFLAGS & RTC_CMP_bm){ \/\/ check for CMP interrupt\r\n RTC.INTFLAGS = RTC_CMP_bm; \/\/ delete CMP interrupt flag\r\n PORTA.OUTCLR = PIN2_bm; \/\/ PA2 = LOW\r\n }\r\n if(RTC.INTFLAGS & RTC_OVF_bm){ \/\/ check for OVF interrupt\r\n RTC.INTFLAGS = RTC_OVF_bm; \/\/ delete OVF interrupt flag\r\n PORTA.OUTSET = PIN2_bm; \/\/ PA2 = HIGH\r\n }\r\n}\r\n\r\nvoid setup() {\r\n delay(1);\r\n PORTA.DIRSET = PIN2_bm;\r\n RTC.CLKSEL = RTC_CLKSEL_INT32K_gc; \/\/ set internal clock @ 32768 Hz\r\n RTC.PER = 16383; \/\/ TOP = 16383\r\n RTC.CMP = 12288; \/\/ Compare value = 12288\r\n RTC.INTCTRL = RTC_CMP_bm | RTC_OVF_bm; \/\/ enable CMP and OVF interrupts\r\n RTC.CTRLA = RTC_PRESCALER_DIV4_gc | RTC_RTCEN_bm; \/\/ Prescaler = 4 and enable RTC\r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nPIT example sketch 1<\/h4>\n\n
ISR(RTC_PIT_vect){\r\n RTC.PITINTFLAGS = RTC_PI_bm; \/\/ clear PIT interrupt flag\r\n PORTA.OUTTGL = PIN2_bm; \/\/ toggle PA2\r\n}\r\n\r\nvoid setup() {\r\n PORTA.DIRSET = PIN2_bm;\r\n RTC.CLKSEL = RTC_CLKSEL_INT32K_gc; \/\/ set internal clock @ 32768 Hz\r\n RTC.PITINTCTRL = RTC_PI_bm; \/\/ enable PIT interrupt\r\n RTC.PITCTRLA = RTC_PERIOD_CYC16384_gc | RTC_PITEN_bm; \/\/ interrupt frq.: 2 Hz\r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nPIT example sketch 2<\/h4>\n\n
void setup() {\r\n PORTA.DIRSET = PIN2_bm;\r\n RTC.CLKSEL = RTC_CLKSEL_INT1K_gc; \/\/ set internal clock @ 1.024 kHz\r\n RTC.PITCTRLA = RTC_PITEN_bm; \r\n PORTMUX.CTRLA |= PORTMUX_EVOUT0_bm; \/\/ Event output needs to be enabled for tinyAVR 0\/1\r\n EVSYS.ASYNCCH3 = EVSYS_ASYNCCH3_PIT_DIV1024_gc; \/\/ Event freq. = 1024 \/ 1024 = 1 [Hz]\r\n EVSYS.ASYNCUSER8 = EVSYS_ASYNCUSER8_ASYNCCH3_gc;\r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nWatchdog Timer – WDT Module<\/h2>\n\n
The registers of the WDT Module<\/h3>\n\n
\r\n
Control A Register CTRLA<\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_WDT_CTRLA-1024x81.webp\")
<\/a>![\"WINDOW[3:0]](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/wdt_ctrla_settings-1024x404.webp\")
<\/a>\r\n
wdt_reset()<\/code>, the WDT is in the period defined by WINDOW. The data sheet calls this period “closed window time-out period” (TOWDTW<\/sub>). The WDT cannot be reset during this period. A wdt_reset()<\/code> within this period leads to an immediate system reset.<\/li>\r\nwdt_reset()<\/code> is received during this time, the game starts again from the beginning with the TOWDTW<\/code>.<\/li>\r\nwdt_reset()<\/code> in the TOWDTW<\/sub> + TOWDT<\/sub> period, a system reset is carried out.<\/li>\r\n<\/ul>\r\n\nStatus Register STATUS <\/h4>\n\n
![\"tinyAVR](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_WDT_STATUS-1024x80.webp\")
<\/a>Example Sketch for the WDT<\/h3>\n\n
#include <avr\/wdt.h>\r\nvoid setup(){\r\n Serial.begin(115200);\r\n Serial.println(\"*******************\");\r\n Serial.println(\"Watchdog Timer Test\");\r\n Serial.println(\"Sketch starts...\");\r\n CPU_CCP = CCP_IOREG_gc; \/\/ allow changes\r\n WDT.CTRLA = WDT_WINDOW_4KCLK_gc | WDT_PERIOD_4KCLK_gc; \/\/ 4s period and window\r\n CPU_CCP = CCP_IOREG_gc;\r\n WDT.STATUS = WDT_LOCK_bm;\r\n while(WDT.STATUS & WDT_SYNCBUSY_bm){} \/\/ wait until WDT is synchronized\r\n wdt_reset();\r\n int seconds = 0;\r\n while(seconds < 100){\r\n \/\/ if(seconds == 5){ \/\/ try also 3\r\n \/\/ wdt_reset();\r\n \/\/ }\r\n Serial.print(seconds);\r\n Serial.println(\" seconds\");\r\n delay(1000);\r\n seconds++;\r\n }\r\n}\r\n\r\nvoid loop(){}<\/pre>\r\n\nWDT<\/code> = 8 seconds have passed. The last output is “7 seconds” because once the eighth second has been reached, there is no more time for the output of “8 seconds”.<\/p>\r\nwdt_reset()<\/code> at fifth second, i.e. in the “allowed” TOWDT<\/sub> period. The WDT then runs for a further eight seconds until the system reset is carried out.<\/p>\r\nwdt_reset()<\/code> occurs after three seconds, there will be an immediate system reset as you are in the “forbidden” TOWDTW<\/sub> period.<\/p>\r\n\n![\"Output](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/output_wdt_sketch.webp\")
<\/a>A\/D Converter – ADCn Module<\/h2>\n\n
ADCn of the tinyAVR series 0\/1<\/h3>\n\n
![\"Register](\"https:\/\/wolles-elektronikkiste.de\/wp-content\/uploads\/2023\/11\/Reg_Summary_ADC-1.webp\")
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