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/*
ws2812x_dma_timer.ino - DMA/TIMER based ws281x/neopixel routines
Generate a ws281x compatible pulse train using PWM timer and DMA
provided duty cycle data. Connect pin PA1 to the DIN of a ws281x
led strip and watch the animation.
2018-07-07 - RRK simplified using RGB values, compute T0/T1 based on F_CPU
2018-07-05 - RRK reworked to avoid interrupt
*/
#include <libmaple/dma.h>
#define LED_CNT 4 /* I'm using a 4 pixel led strip, change to suit */
#if 0
// you can pick an alternate WS281X pin (default is PA1)
#elif 0
static const int WS281X_PIN = PB0;
#define DMA_REQ_SRC_TIMX_CHNX DMA_REQ_SRC_TIM3_CH3
#define TIMER_DMA_BASE_CCRX TIMER_DMA_BASE_CCR3
#define DMA_CHX DMA_CH2
#elif 0
static const int WS281X_PIN = PB1;
#define DMA_REQ_SRC_TIMX_CHNX DMA_REQ_SRC_TIM3_CH4
#define TIMER_DMA_BASE_CCRX TIMER_DMA_BASE_CCR4
#define DMA_CHX DMA_CH3
#elif 0
static const int WS281X_PIN = PB7;
#define DMA_REQ_SRC_TIMX_CHNX DMA_REQ_SRC_TIM4_CH2
#define TIMER_DMA_BASE_CCRX TIMER_DMA_BASE_CCR2
#define DMA_CHX DMA_CH4
#elif 1
static const int WS281X_PIN = PA1;
#define DMA_REQ_SRC_TIMX_CHNX DMA_REQ_SRC_TIM2_CH2
#define TIMER_DMA_BASE_CCRX TIMER_DMA_BASE_CCR2
#define DMA_CHX DMA_CH7
#elif 0
static const int WS281X_PIN = PA8;
#define DMA_REQ_SRC_TIMX_CHNX DMA_REQ_SRC_TIM1_CH1
#define TIMER_DMA_BASE_CCRX TIMER_DMA_BASE_CCR1
#define DMA_CHX DMA_CH2
#endif
// helpers
#define sizeofs(a) (sizeof(a)/sizeof(a[0]))
#define RGB(r,g,b) g,r,b
#define T800 (F_CPU/800000)
#define TT (T800-1) /* ~1.25us */
#define T1 (uint8_t)((float)T800*.56f) /* ~700ns */
#define T0 (uint8_t)((float)T800*.28f) /* ~350ns */
#define DMA_BUF_SIZE (LED_CNT*24)+1 /* one zero entry so the PWM pin stays low at DMA completion */
//----------------------------------------------------------------------
// global data
timer_dev *ws281x_timer = PIN_MAP[WS281X_PIN].timer_device;
uint8_t dma_buffer[DMA_BUF_SIZE];
dma_tube_config dma_cfg = {
.tube_src = dma_buffer,
.tube_src_size = DMA_SIZE_8BITS,
.tube_dst = &(ws281x_timer->regs.gen->DMAR),
.tube_dst_size = DMA_SIZE_16BITS,
.tube_nr_xfers = DMA_BUF_SIZE,
.tube_flags = DMA_CFG_SRC_INC /* | DMA_CFG_CIRC | DMA_CFG_CMPLT_IE */,
.target_data = 0,
.tube_req_src = DMA_REQ_SRC_TIMX_CHNX
};
//----------------------------------------------------------------------
//
void setup() {
pinMode(WS281X_PIN, PWM);
pinMode(LED_BUILTIN, OUTPUT);
digitalWrite(LED_BUILTIN, LOW);
dma_conf();
timer_conf();
}
void loop() {
// animation frames - marching B,W,R,G colors
static const uint8_t frames[][LED_CNT * 3] = {
{ RGB(0, 0, 0x1f), RGB(0x1f, 0x1f, 0x1f), RGB(0x1f, 0, 0), RGB(0, 0x1f, 0) },
{ RGB(0x1f, 0x1f, 0x1f), RGB(0x1f, 0, 0), RGB(0, 0x1f, 0), RGB(0, 0, 0x1f) },
{ RGB(0x1f, 0, 0), RGB(0, 0x1f, 0), RGB(0, 0, 0x1f), RGB(0x1f, 0x1f, 0x1f) },
{ RGB(0, 0x1f, 0), RGB(0, 0, 0x1f), RGB(0x1f, 0x1f, 0x1f), RGB(0x1f, 0, 0) }
};
unsigned indx = 0;
while (indx < sizeofs(frames)) {
init_dma_buffer(frames[indx++], dma_buffer, LED_CNT * 3);
dma_start();
// wait for DMA completion flag or abort after 100msec timeout
// this normally should take less than 150 usecs for 4 leds
const uint32_t m = millis();
while ( !(dma_get_isr_bits(DMA1, DMA_CHX) & DMA_ISR_TCIF1) ) {
if ((millis() - m) > 100) {
break;
}
}
on_dma_complete();
delay(250);
}
}
//----------------------------------------------------------------------
//
void init_dma_buffer(const uint8_t * const src_pixel_data, uint8_t * dst_pulse_data, unsigned cnt)
{
unsigned bufindx = 0;
for (unsigned led = 0; led < cnt ; ++led) {
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 7)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 6)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 5)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 4)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 3)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 2)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 1)) ? T1 : T0;
dst_pulse_data[bufindx++] = (src_pixel_data[led] & (1 << 0)) ? T1 : T0;
}
}
//----------------------------------------------------------------------
//
void dma_conf()
{
dma_init(DMA1);
}
void dma_start()
{
// dma_tube_cfg() - disables DMA, clears ISR flags and sets DMA src,dest,and count
if ( dma_tube_cfg(DMA1, DMA_CHX, &dma_cfg) != DMA_TUBE_CFG_SUCCESS) {
while (1); // trap DMA config error here
}
dma_enable(DMA1, DMA_CHX);
timer_resume(ws281x_timer);
}
void on_dma_complete()
{
timer_pause(ws281x_timer);
dma_disable(DMA1, DMA_CHX);
GPIOC->regs->ODR ^= 1 << 13; // toggle builtin_led
}
//----------------------------------------------------------------------
//
void timer_conf()
{
timer_dma_set_base_addr(ws281x_timer, TIMER_DMA_BASE_CCRX);
timer_dma_set_burst_len(ws281x_timer, 1);
timer_dma_enable_req(ws281x_timer, PIN_MAP[WS281X_PIN].timer_channel);
timer_set_prescaler(ws281x_timer, 0);
timer_set_reload(ws281x_timer, TT); // 72000000/800000-1 == 800k period
}
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