Okay, time to jump straight into Arduino AVR microcontroller
development head-first. I’ve got the simavr simulator right here,
so I can start coding. How do I compile? Yes, the hint right there,
use avr-gcc and avr-libc. And how do I use the compiler
specifically to produce ATTiny85 firmware? Just like this.
avr-gcc -o MacPlusRTC.axf -Os -mmcu=attiny85 MacRTC.c
20200904/https://github.com/buserror/simavr
20200905/https://raw.githubusercontent.com/buserror/simavr/master/doc/manual/manual.pdf
20200905/DuckDuckGo attiny blink demo code
20200905/https://www.instructables.com/id/Attiny85-USB-Development-Board-LED-Blinking-With-A/
20200905/DuckDuckGo gcc avr
20200905/DuckDuckGo gcc avr attiny
20200905/https://github.com/vladbelous/tinyAVR_gcc_setup
20200905/http://www.lightner.net/avr/ATtinyAvrGcc.html
20200905/https://www.digikey.com/product-detail/en/microchip-technology/ATTINY85-20PU/ATTINY85-20PU-ND/735469
20200905/https://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet-Summary.pdf
20200905/http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-2586-AVR-8-bit-Microcontroller-ATtiny25-ATtiny45-ATtiny85_Datasheet.pdf
But Arduino sketches don’t compile with avr-gcc, the library
functions they are using are missing. But surely, looking at them,
they’re simple macros, easy to include straight into your source code,
right?
So, yes, the source code for the Arduino library functions is on
GitHub, you say? Indeed it is, it really is just plain C source code
with copying and pasting headers and footers, look over here. Now I
can look at these and use them to transform Arduino sketches into
vanilla C source code that compiles with avr-gcc.
20200905/https://en.wikipedia.org/wiki/Wiring_(development_platform)
20200905/https://github.com/arduino/Arduino
20200905/https://github.com/arduino/ArduinoCore-avr
20200905/https://github.com/arduino/ArduinoCore-avr/tree/master/cores/arduino
20200905/https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/Arduino.h
20200905/https://github.com/arduino/ArduinoCore-avr/blob/master/cores/arduino/wiring_digital.c
20200905/https://github.com/arduino/ArduinoCore-avr/tree/master/variants
Okay, but I’m not seeing ATTiny85 pin mappings in the Arduino source code. But surely, it must be possible if this source code was using the technique. Maybe there’s a ATTiny85 plugin for Arduino Studio? Indeed there is.
20200905/DuckDuckGo attiny arduino studio
20200905/https://www.arrow.com/en/research-and-events/articles/attiny85-arduino-tutorial
20200905/DuckDuckGo arduino attiny github
20200905/https://github.com/damellis/attiny
20200905/https://github.com/damellis/attiny/blob/master/variants/tiny8/pins_arduino.h
How to update fuse bits on AVR microcontrollers, you can’t include it in your same standard firmware image, you need to use a separate special command, but at least it can still be scripted.
20200904/DuckDuckGo avr-gcc flash fuse bits
20200904/https://www.instructables.com/id/AVR-Microcontroller-Fuse-Bits-Configuration-Creati/
The ATTiny85 only has one pin change interrupt service routine. Is there any register that indicates which pin changed? Looks like there isn’t, you just have to monitor the pin values and do the change detection yourself, which purportedly isn’t hard since there are so few pins.
20200905/DuckDuckGo pcint0 source
20200905/https://arduino.stackexchange.com/questions/70348/pcint0-pcint1-pcint2-etc-on-attiny45-85
Can you do open-drain signaling with an AVR? Yes you can, you simply change a pin to an input-no-pullup when you want it to be high-impedance. Yes, just like I thought.
20200905/DuckDuckGo avr open drain pin
20200905/https://www.avrfreaks.net/forum/open-drain-0
However, for multiple pin change interrupts on the ATMega 328, there is indeed the PCIFR register where the bits will be set based off of which pin triggers the pin change interrupt. Very useful to have that information at your disposal.
20200905/DuckDuckGo avr interrupt pin change source flag register
20200905/https://www.avrfreaks.net/forum/pin-change-interrupt-atmega328p
But hey, actually there’s an important note here when using timers. I was searching to try to solve my problem of timer slipping. But, anyways, when configuring the timer registers, to be on the safe side, make sure you set all bits, else you don’t know that they might not be properly defined. Though I’d reckon, of course they have to be properly zeroed to sane values on RESET.
20200906/DuckDuckGo avr generate one second wave
20200906/https://www.avrfreaks.net/forum/generating-square-wave-0