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neopixel improvements for esp8266

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Thorsten von Eicken 2015-12-18 17:39:40 -08:00
parent a4ec9fa2b8
commit 9bf51d3c8b
1 changed files with 44 additions and 0 deletions
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44
targets/esp8266/jswrap_esp8266.c
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@ -328,6 +328,49 @@ void jswrap_ESP8266_neopixelWrite(Pin pin, JsVar *jsArrayOfData) {
return;
}
if (!jshGetPinStateIsManual(pin))
jshPinSetState(pin, JSHPINSTATE_GPIO_OUT);
#if 1
// the loop over the RGB pixel bits below is loaded into the instruction cache from flash
// with the result that dependeing on the cache line alignment the first loop iteration
// takes too long and thereby messes up the first LED.
// The fix is to make it so the first loop iteration does nothing, i.e. just outputs the
// same "low" for the full loop as we had before entering this function. This way no LED
// gets set to the wrong value and we load the cache line so the second iteration, i.e.,
// first real LED bit, runs at full speed.
uint32_t pinMask = _BV(pin); // bit mask for GPIO pin to write to reg
uint8_t *p = (uint8_t *)pixels; // pointer to walk through pixel array
uint8_t *end = p + dataLength; // pointer to end of array
uint8_t pix = *p++; // current byte being shifted out
uint8_t mask = 0x80; // mask for current bit
uint32_t start; // start time of bit
// adjust things for the pre-roll
p--; // next byte we fetch will be the first byte again
mask = 0x01; // fetch the next byte at the end of the first loop iteration
pinMask = 0; // zero mask means we set or clear no I/O pin
// iterate through all bits
ets_intr_lock(); // disable most interrupts
while(1) {
uint32_t t;
if (pix & mask) t = 56; // one bit, high typ 800ns (56 cyc = 700ns)
else t = 14; // zero bit, high typ 300ns (14 cycl = 175ns)
GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, pinMask); // Set high
start = _getCycleCount(); // get start time of this bit
while (_getCycleCount()-start < t) ; // busy-wait
GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, pinMask); // Set low
if (!(mask >>= 1)) { // Next bit/byte?
if (p >= end) break; // at end, we're done
pix = *p++;
mask = 0x80;
pinMask = _BV(pin);
}
while (_getCycleCount()-start < 100) ; // busy-wait, 100 cyc = 1.25us
}
while (_getCycleCount()-start < 100) ; // Wait for last bit
ets_intr_unlock();
#else
// this is the code without preloading the first bit
uint32_t pinMask = _BV(pin); // bit mask for GPIO pin to write to reg
uint8_t *p = (uint8_t *)pixels; // pointer to walk through pixel array
uint8_t *end = p + dataLength; // pointer to end of array
@ -351,6 +394,7 @@ void jswrap_ESP8266_neopixelWrite(Pin pin, JsVar *jsArrayOfData) {
while (_getCycleCount()-start < 100) ; // busy-wait, 100 cyc = 1.25us
}
while (_getCycleCount()-start < 100) ; // Wait for last bit
#endif
// at some point the fact that the code above needs to be loaded from flash to cache caused the
// first bit's timing to be off. If this recurs, a suggestion is to run a loop iteration