Possibly different frequency for bootloader and user code?

[TheLastGimbus]

I wanted to reduce power consumption of my board - one of the options is to reduce the clock speed

Sadly, looks like USB comm (and thus, this bootloader) require 12MHz at least - legit 💯

But I don't plan using usb in my Arduino code tho... would it be ever possible to have different clock in bootloader and user code?

[cpldcpu]

That is easily possible now. Just change the clockspeed in your user program.

[TheLastGimbus]

Looks like i can do this with:

#include <avr/power.h>
clock_prescale_set(clock_div_8);

But delay() is now also 8 times slower 😂 - same as the guy here: https://forum.arduino.cc/t/arduino-1-0-6-attiny-85-delay-much-longer-why/271052

Ps. setting #define F_CPU 2062500 (16500000/8) at the very top of main.cpp file doesn't help at all 😞

Pps. millis() based s

[cpldcpu]

seems to be explained here:

https://forum.arduino.cc/t/problem-with-define-f_cpu/455431/3

[TheLastGimbus]

Huh... thanks! From all of this, I thought "ok, so maybe I just have to tell platformio to compile everything with different frequency 🤔 "

But, if I compile stuff with board_build.f_cpu anything other than 16000000 or 8000000, it panicks and screams (surely FastLED.h does)... and micronucleus (without extra crystal) supports only 12.5 and 16.5... so I would have timing a bit off, but not as much...

Well, in my case, it may be just not really do-able, but someone else could try this for sure!

[ArminJo]

Use e.g. https://github.com/SpenceKonde/ATTinyCore and choose the desired program frequency (F_CPU). The core sets the frequency after the bootloader and before your setup to the right value.

[TheLastGimbus]

Hm... as I understand, this is some alternative Arduino core for attiny? Looks interesting :eyes; however, I don't have enought curage to try it now, so can't tell if it woks :/

Could you tell me if this would increase the flash size usage? Or would even decrease it 🤔 ?