ATtiny85 runs at half speed due to bad clock source setting

[Granjow]

Commit 012de336af56472e65e2db2e6c2d95d9a137803d, which was released with version 3.4.0, breaks ATtiny support when using frequencies other than 16 MHz. When setting board_build.f_cpu = 8000000L, the code is still compiled for 16 MHz due to the clock source and therefore the code only runs half as fast.

I don't know where the correct place to fix #255 is, but the attiny85.json definitely isn't because it is not even possible to override the clock source setting with board_build.clocksource = 0. A local workaround would probably be to set board_build.clocksource = 6 e.g. for the ATtiny85 in the platformio.ini.

[rholder]

@Granjow Thanks for the detailed description here as it helped me get a project build fixed much faster than I expected. I've opened up a PR with your suggested change.

[valeros]

Hi @Granjow @rholder ! Thanks for reporting, should be fixed in the dev branch. Please retest with the upstream version of the platform:

[env:attiny85]
platform = https://github.com/platformio/platform-atmelavr.git
framework = arduino
board = attiny85

I don't know where the correct place to fix #255 is, but the attiny85.json definitely isn't because it is not even possible to override the clock source setting with board_build.clocksource = 0.

It's was possible to override simply by specifying your own define -DCLOCK_SOURCE=0. Anyway, as you requested, it's now also possible to configure these settings via the board configuration:

[env:attiny85]
platform = atmelavr
framework = arduino
board = attiny85
board_build.f_cpu = 16000000L
board_build.clock_source = 6

[Granjow]

@rholder Glad to hear!

@valeros Thanks a lot for the fix! Can I use pio platform install to test the upstream version?

[valeros]

@Granjow Yes, simply run pio platform install https://github.com/platformio/platform-atmelavr.git, but to avoid any conflicts I'd recommend to delete the stable version beforehand.

[Granjow]

@valeros That worked. Can confirm that with this patch the problem is solved and the ATtiny85 now runs as expected. Thanks again!

[ikatkov]

For people who came here from a websearch if your attyiny85 runs at half speed through Platformio and works fine through Arduino IDE

• either switch to the dev version of the platform-atmelavr
• or edit your local file in $HOME/.platformio/platforms/atmelavr/boards/attiny85.json and remove "-DNEOPIXELPORT=PORTB -DCLOCK_SOURCE=6"

I'd assume that the next release will fix it, but until then these are your only options

[ur99999999]

temporary fix: add next line to platformio.ini [env:...] build_flags = -DCLOCK_SOURCE=0