mirror of
https://github.com/tinygo-org/drivers.git
synced 2026-07-26 10:38:41 +00:00
Ayke van Laethem
715c33d4b0
For details, see: https://github.com/tinygo-org/tinygo/pull/3927 This change just means we need to be more careful to use the right type, now that types like C.uint32_t don't match to the Go equivalent (like uint32).
71 lines
2.2 KiB
Go
71 lines
2.2 KiB
Go
//go:build avr
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package ws2812
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// This file implements the WS2812 protocol for AVR microcontrollers.
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import (
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"machine"
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"runtime/interrupt"
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"unsafe"
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)
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/*
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#include <stdint.h>
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__attribute__((always_inline))
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void ws2812_writeByte16(char c, uint8_t *port, uint8_t maskSet, uint8_t maskClear) {
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// See:
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// https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
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// T0H: 4 cycles or 250ns
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// T0L: 14 cycles or 875ns -> together 18 cycles or 1125ns
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// T1H: 9 cycles or 562ns
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// T1L: 8 cycles or 500ns -> together 17 cycles or 1062ns
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char i = 8;
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__asm__ __volatile__(
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"1:\n"
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"\t st %[port], %[maskSet] ; [2] set output high\n"
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"\t lsl %[value] ; [1] shift off the next bit, store it in C\n"
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"\t brcs 2f ; [1/2] branch if this bit is high (long pulse)\n"
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"\t st %[port], %[maskClear] ; [2] set output low (short pulse)\n"
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"\t2:\n"
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"\t nop ; [4] wait before changing the output again\n"
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"\t nop\n"
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"\t nop\n"
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"\t nop\n"
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"\t st %[port], %[maskClear] ; [2] set output low (end of pulse)\n"
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"\t nop ; [3]\n"
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"\t nop\n"
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"\t nop\n"
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"\t subi %[i], 1 ; [1] subtract one (for the loop)\n"
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"\t brne 1b ; [1/2] send the next bit, if not at the end of the loop\n"
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: [value]"+r"(c),
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[i]"+r"(i)
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: [maskSet]"r"(maskSet),
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[maskClear]"r"(maskClear),
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[port]"m"(*port));
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}
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*/
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import "C"
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// Send a single byte using the WS2812 protocol.
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func (d Device) WriteByte(c byte) error {
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// On AVR, the port is always the same for setting and clearing a register
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// so use only one. This avoids the following error:
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// error: inline assembly requires more registers than available
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// Probably this is about pointer registers, which are very limited on AVR.
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port, maskSet := d.Pin.PortMaskSet()
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_, maskClear := d.Pin.PortMaskClear()
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mask := interrupt.Disable()
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switch machine.CPUFrequency() {
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case 16e6: // 16MHz
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C.ws2812_writeByte16(C.char(c), (*C.uint8_t)(unsafe.Pointer(port)), C.uint8_t(maskSet), C.uint8_t(maskClear))
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interrupt.Restore(mask)
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return nil
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default:
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interrupt.Restore(mask)
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return errUnknownClockSpeed
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}
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}
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