tinygo-org/drivers
1
0
Fork 0
mirror of https://github.com/tinygo-org/drivers.git synced 2026-08-03 06:27:47 +00:00
Code Issues Packages Projects Releases 10 Wiki Activity

ws2812: add support for the Xtensa architecture

Browse Source 
This allows WS2812 LEDs to be controlled by an ESP32. Right now it only
supports 160MHz operation, which is the default with current ESP32
support in TinyGo.
This commit is contained in:
Ayke van Laethem
2020-09-05 01:19:27 +02:00
committed by Ron Evans
parent 705f474897
commit 7cd7df7bb8
1 changed files with 230 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files
ws2812/ws2812_xtensa.go
+230
View File
@@ -0,0 +1,230 @@
// +build xtensa
package ws2812
import (
"device"
"errors"
"machine"
"unsafe"
)
var errUnknownClockSpeed = errors.New("ws2812: unknown CPU clock speed")
func (d Device) WriteByte(c byte) error {
portSet, maskSet := d.Pin.PortMaskSet()
portClear, maskClear := d.Pin.PortMaskClear()
switch machine.CPUFrequency() {
case 160e6:
// See:
// https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
// Because I do not know the exact instruction timings, I'm going to
// assume that every instruction executes in one cycle. Branches and
// load/stores will probably be slower than that, but as long as all
// timings are only increased a little bit this should not be a problem
// (see above post).
// T0H: 40 cycles or 333.3ns
// T0L: 131 cycles or 1091.7ns
// +: 171 cycles or 1425.0ns
// T1H: 95 cycles or 791.7ns
// T1L: 75 cycles or 625.0ns
// +: 170 cycles or 1416.7ns
// Some documentation:
// http://cholla.mmto.org/esp8266/xtensa.html
// https://0x04.net/~mwk/doc/xtensa.pdf
device.AsmFull(`
1: // send_bit
s32i {maskSet}, {portSet}, 0 // [1] T0H and T1H start here
nop // [37]
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
slli {value}, {value}, 1 // [1] shift {value} to the left by 1
bbsi {value}, 8, 2f // [1] branch to skip_store if bit 8 is set
s32i {maskClear}, {portClear}, 0 // [1] T0H -> T0L transition
2: // skip_store
nop // [55]
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
s32i {maskClear}, {portClear}, 0 // [1] T1H -> T1L transition
nop // [72]
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
nop
addi {i}, {i}, -1 // [1]
bnez {i}, 1b // [1] send_bit, T1H and T1L end here
// Restore original values after modifying them in the inline
// assembly. Not doing that would result in undefined behavior as
// the compiler doesn't know we're modifying these values.
movi.n {i}, 8
slli {value}, {value}, 8
`, map[string]interface{}{
// Note: casting pointers to uintptr here because of what might be
// an Xtensa backend bug with inline assembly.
"value": uint32(c),
"i": 8,
"maskSet": maskSet,
"portSet": uintptr(unsafe.Pointer(portSet)),
"maskClear": maskClear,
"portClear": uintptr(unsafe.Pointer(portClear)),
})
return nil
default:
return errUnknownClockSpeed
}
}