* machine/attiny85: add PWM support for Timer0 and Timer1
Add complete PWM implementation for ATtiny85, supporting both Timer0
and Timer1 with their respective output channels:
- Timer0: 8-bit timer for pins PB0 (OC0A) and PB1 (OC0B)
- Timer1: 8-bit high-speed timer for pins PB1 (OC1A) and PB4 (OC1B)
Timer1 provides more flexible period control with configurable top value
(OCR1C) and extended prescaler options (1-16384), making it well-suited
for LED PWM control and other applications requiring variable frequencies.
Implements full PWM interface including Configure, SetPeriod, Channel,
Set, SetInverting, Top, Counter, and Period methods.
* machine/digispark: document PWM support on pins
Add documentation to the Digispark board file indicating which pins
support PWM output:
- P0 (PB0): Timer0 channel A
- P1 (PB1): Timer0 channel B or Timer1 channel A
- P4 (PB4): Timer1 channel B
Includes package comment explaining Timer0 vs Timer1 capabilities,
with Timer1 recommended for more flexible frequency control.
* machine/attiny85: optimize PWM prescaler lookups
Replace verbose switch statements with more efficient implementations:
- SetPeriod: Use bit shift (top >>= prescaler-1) instead of 15-case
switch for dividing uint64 by power-of-2 prescaler values
- Period: Replace switch statements with compact uint16 lookup tables
for both Timer0 and Timer1, casting to uint64 only when needed
This addresses review feedback about inefficient switch-based lookups.
On AVR, this approach is significantly smaller:
- Bit shifts for uint64 division: ~34 bytes vs ~140 bytes
- uint16 tables: 22 bytes code + 32/16 bytes data vs ~140 bytes
- Total savings: ~190 bytes (68% reduction)
* examples/pwm: add digispark support and smoketest
Add digispark.go configuration for PWM example using Timer1 with pins P1 (LED) and P4. Also add digispark PWM example to GNUmakefile smoketests.
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Do it all at once in preparation for Go 1.18 support.
To make this commit, I've simply modified the `fmt-check` Makefile
target to rewrite files instead of listing the differences. So this is a
fully mechanical change, it should not have introduced any errors.
Instead of trying to modify periperhals directly, external functions are
called. For example, __tinygo_gpio_set sets a GPIO pin to a specified
value (high or low). It is expected that binaries made this way will be
linked with some extra libraries that implement support for these
functions.
One particularly interesting case is this experimental board simulator:
https://github.com/aykevl/tinygo-play
Compiling code to WebAssembly with the correct build tag for a board
will enable this board to be simulated in the browser.
Atmel/Microchip based SAMD boards are not currently supported, because
their I2C/SPI support is somewhat uncommon and harder to support in the
machine API. They may require a modification to the machine API for
proper support.
Jesús Espino
Yurii Soldak
Ayke van Laethem
Ron Evans