From 3ae24d9f9a36cfba6aeb616abe5aa576ce27d69a Mon Sep 17 00:00:00 2001 From: hathach Date: Tue, 4 Sep 2018 17:02:45 +0700 Subject: [PATCH] add neopixel_write implementation, work ok --- .../nrf/common-hal/neopixel_write/__init__.c | 234 +++++++++++++++++- 1 file changed, 233 insertions(+), 1 deletion(-) diff --git a/ports/nrf/common-hal/neopixel_write/__init__.c b/ports/nrf/common-hal/neopixel_write/__init__.c index c5f6713609..ff2a2fa773 100644 --- a/ports/nrf/common-hal/neopixel_write/__init__.c +++ b/ports/nrf/common-hal/neopixel_write/__init__.c @@ -27,6 +27,238 @@ #include "py/mphal.h" #include "shared-bindings/neopixel_write/__init__.h" -void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout, uint8_t *pixels, uint32_t numBytes) { +// https://github.com/adafruit/Adafruit_NeoPixel/blob/master/Adafruit_NeoPixel.cpp +// [[[Begin of the Neopixel NRF52 EasyDMA implementation +// by the Hackerspace San Salvador]]] +// This technique uses the PWM peripheral on the NRF52. The PWM uses the +// EasyDMA feature included on the chip. This technique loads the duty +// cycle configuration for each cycle when the PWM is enabled. For this +// to work we need to store a 16 bit configuration for each bit of the +// RGB(W) values in the pixel buffer. +// Comparator values for the PWM were hand picked and are guaranteed to +// be 100% organic to preserve freshness and high accuracy. Current +// parameters are: +// * PWM Clock: 16Mhz +// * Minimum step time: 62.5ns +// * Time for zero in high (T0H): 0.31ms +// * Time for one in high (T1H): 0.75ms +// * Cycle time: 1.25us +// * Frequency: 800Khz +// For 400Khz we just double the calculated times. +// ---------- BEGIN Constants for the EasyDMA implementation ----------- +// The PWM starts the duty cycle in LOW. To start with HIGH we +// need to set the 15th bit on each register. +// WS2812 (rev A) timing is 0.35 and 0.7us +//#define MAGIC_T0H 5UL | (0x8000) // 0.3125us +//#define MAGIC_T1H 12UL | (0x8000) // 0.75us + +// WS2812B (rev B) timing is 0.4 and 0.8 us +#define MAGIC_T0H 6UL | (0x8000) // 0.375us +#define MAGIC_T1H 13UL | (0x8000) // 0.8125us +#define CTOPVAL 20UL // 1.25us + +// ---------- END Constants for the EasyDMA implementation ------------- +// +// If there is no device available an alternative cycle-counter +// implementation is tried. +// The nRF52832 runs with a fixed clock of 64Mhz. The alternative +// implementation is the same as the one used for the Teensy 3.0/1/2 but +// with the Nordic SDK HAL & registers syntax. +// The number of cycles was hand picked and is guaranteed to be 100% +// organic to preserve freshness and high accuracy. +// ---------- BEGIN Constants for cycle counter implementation --------- +#define CYCLES_800_T0H 18 // ~0.36 uS +#define CYCLES_800_T1H 41 // ~0.76 uS +#define CYCLES_800 71 // ~1.25 uS + +// ---------- END of Constants for cycle counter implementation -------- + +// find a free PWM device, which is not enabled and has no connected pins +static NRF_PWM_Type* find_free_pwm (void) { + NRF_PWM_Type* PWM[3] = { NRF_PWM0, NRF_PWM1, NRF_PWM2 }; + + for ( int device = 0; device < 3; device++ ) { + if ( (PWM[device]->ENABLE == 0) && (PWM[device]->PSEL.OUT[0] & PWM_PSEL_OUT_CONNECT_Msk) + && (PWM[device]->PSEL.OUT[1] & PWM_PSEL_OUT_CONNECT_Msk) + && (PWM[device]->PSEL.OUT[2] & PWM_PSEL_OUT_CONNECT_Msk) + && (PWM[device]->PSEL.OUT[3] & PWM_PSEL_OUT_CONNECT_Msk) ) { + return PWM[device]; + } + } + + return NULL; +} + +void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout, uint8_t *pixels, uint32_t numBytes) { + // To support both the SoftDevice + Neopixels we use the EasyDMA + // feature from the NRF25. However this technique implies to + // generate a pattern and store it on the memory. The actual + // memory used in bytes corresponds to the following formula: + // totalMem = numBytes*8*2+(2*2) + // The two additional bytes at the end are needed to reset the + // sequence. + // + // If there is not enough memory, we will fall back to cycle counter + // using DWT + uint32_t pattern_size = numBytes * 8 * sizeof(uint16_t) + 2 * sizeof(uint16_t); + uint16_t* pixels_pattern = NULL; + + NRF_PWM_Type* pwm = find_free_pwm(); + + // only malloc if there is PWM device available + if ( pwm != NULL ) { + pixels_pattern = (uint16_t *) m_malloc(pattern_size, false); + } + + // Use the identified device to choose the implementation + // If a PWM device is available use DMA + if ( (pixels_pattern != NULL) && (pwm != NULL) ) { + uint16_t pos = 0; // bit position + + for ( uint16_t n = 0; n < numBytes; n++ ) { + uint8_t pix = pixels[n]; + + for ( uint8_t mask = 0x80, i = 0; mask > 0; mask >>= 1, i++ ) { + pixels_pattern[pos] = (pix & mask) ? MAGIC_T1H : MAGIC_T0H; + pos++; + } + } + + // Zero padding to indicate the end of sequence + pixels_pattern[++pos] = 0 | (0x8000); // Seq end + pixels_pattern[++pos] = 0 | (0x8000); // Seq end + + // Set the wave mode to count UP + pwm->MODE = (PWM_MODE_UPDOWN_Up << PWM_MODE_UPDOWN_Pos); + + // Set the PWM to use the 16MHz clock + pwm->PRESCALER = (PWM_PRESCALER_PRESCALER_DIV_1 << PWM_PRESCALER_PRESCALER_Pos); + + // Setting of the maximum count + // but keeping it on 16Mhz allows for more granularity just + // in case someone wants to do more fine-tuning of the timing. + pwm->COUNTERTOP = (CTOPVAL << PWM_COUNTERTOP_COUNTERTOP_Pos); + + // Disable loops, we want the sequence to repeat only once + pwm->LOOP = (PWM_LOOP_CNT_Disabled << PWM_LOOP_CNT_Pos); + + // On the "Common" setting the PWM uses the same pattern for the + // for supported sequences. The pattern is stored on half-word + // of 16bits + pwm->DECODER = (PWM_DECODER_LOAD_Common << PWM_DECODER_LOAD_Pos) + | (PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos); + + // Pointer to the memory storing the patter + pwm->SEQ[0].PTR = (uint32_t) (pixels_pattern) << PWM_SEQ_PTR_PTR_Pos; + + // Calculation of the number of steps loaded from memory. + pwm->SEQ[0].CNT = (pattern_size / sizeof(uint16_t)) << PWM_SEQ_CNT_CNT_Pos; + + // The following settings are ignored with the current config. + pwm->SEQ[0].REFRESH = 0; + pwm->SEQ[0].ENDDELAY = 0; + + // The Neopixel implementation is a blocking algorithm. DMA + // allows for non-blocking operation. To "simulate" a blocking + // operation we enable the interruption for the end of sequence + // and block the execution thread until the event flag is set by + // the peripheral. + // pwm->INTEN |= (PWM_INTEN_SEQEND0_Enabled<PSEL.OUT[0] = ( digitalinout->pin->port*32 + digitalinout->pin->pin ); + + // Enable the PWM + pwm->ENABLE = 1; + + // After all of this and many hours of reading the documentation + // we are ready to start the sequence... + pwm->EVENTS_SEQEND[0] = 0; + pwm->TASKS_SEQSTART[0] = 1; + + // But we have to wait for the flag to be set. + while ( !pwm->EVENTS_SEQEND[0] ) { +//#ifdef MICROPY_VM_HOOK_LOOP +// MICROPY_VM_HOOK_LOOP +//#endif + } + + // Before leave we clear the flag for the event. + pwm->EVENTS_SEQEND[0] = 0; + + // We need to disable the device and disconnect + // all the outputs before leave or the device will not + // be selected on the next call. + // TODO: Check if disabling the device causes performance issues. + pwm->ENABLE = 0; + pwm->PSEL.OUT[0] = 0xFFFFFFFFUL; + + m_free(pixels_pattern); + } // End of DMA implementation + // --------------------------------------------------------------------- + else { + // Fall back to DWT + // If you are using the Bluetooth SoftDevice we advise you to not disable + // the interrupts. Disabling the interrupts even for short periods of time + // causes the SoftDevice to stop working. + // Disable the interrupts only in cases where you need high performance for + // the LEDs and if you are not using the EasyDMA feature. + __disable_irq(); + + NRF_GPIO_Type* port = ( digitalinout->pin->port ? NRF_P1 : NRF_P0 ); + uint32_t pinMask = ( 1UL << digitalinout->pin->pin ); + + uint32_t CYCLES_X00 = CYCLES_800; + uint32_t CYCLES_X00_T1H = CYCLES_800_T1H; + uint32_t CYCLES_X00_T0H = CYCLES_800_T0H; + + // Enable DWT in debug core + CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk; + DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk; + + // Tries to re-send the frame if is interrupted by the SoftDevice. + while ( 1 ) { + uint8_t *p = pixels; + + uint32_t cycStart = DWT->CYCCNT; + uint32_t cyc = 0; + + for ( uint16_t n = 0; n < numBytes; n++ ) { + uint8_t pix = *p++; + + for ( uint8_t mask = 0x80; mask; mask >>= 1 ) { + while ( DWT->CYCCNT - cyc < CYCLES_X00 ) + ; + cyc = DWT->CYCCNT; + + port->OUTSET |= pinMask; + + if ( pix & mask ) { + while ( DWT->CYCCNT - cyc < CYCLES_X00_T1H ) + ; + } else { + while ( DWT->CYCCNT - cyc < CYCLES_X00_T0H ) + ; + } + + port->OUTCLR |= pinMask; + } + } + while ( DWT->CYCCNT - cyc < CYCLES_X00 ) + ; + + // If total time longer than 25%, resend the whole data. + // Since we are likely to be interrupted by SoftDevice + if ( (DWT->CYCCNT - cycStart) < (8 * numBytes * ((CYCLES_X00 * 5) / 4)) ) { + break; + } + + // re-send need 300us delay + mp_hal_delay_us(300); + } + + // Enable interrupts again + __enable_irq(); + } }