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Jesús Espino
d62dda8140
* 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. ---------