Add RMT DMA support

main/main.cpp

@@ -107,7 +107,7 @@ extern "C" void app_main(void) {
     // ScreenLEDs()
     // SPI_LEDs(39);
     // RMT_LEDs(GPIO_NUM_17);
-    LEDStrip *LEDs = new RMT_LEDs(GPIO_NUM_17);
+    LEDStrip *LEDs = new RMT_LEDs(17);
     int frequency = 30;
 
     while (true) {

main/rmt_leds.cpp

@@ -7,98 +7,189 @@ static const char *TAG = "rmt_leds";
 #include "rmt_leds.hpp"
 
 
-#define WS2811_PULSE_WIDTH_NS 1250
+#define WS2811_PULSE_WIDTH_NS 833
+#define WS2811_RESET_WIDTH_US 300
 
-#define RMT_TX_CHANNEL RMT_CHANNEL_0
+// Each pulse is divided into thirds - two high / one low for 1, vice versa for 0
+#define SHORT_TICKS 1
+#define LONG_TICKS  2
+#define BIT_TICKS (SHORT_TICKS + LONG_TICKS)
+#define RMT_RESOLUTION_HZ ((BIT_TICKS * (uint64_t)1e9) / WS2811_PULSE_WIDTH_NS)
+#define RESET_TICKS ((RMT_RESOLUTION_HZ * WS2811_RESET_WIDTH_US) / (uint32_t)1e6)
 
+// Use RMT CHannel 3 for TX + DMA
+#define RMT_TX_CHANNEL RMT_CHANNEL_3
 
-static int bit_ticks;
 
-
-static void IRAM_ATTR ws2811_rmt_adapter(
-            const void *src, rmt_item32_t *dest, size_t src_size,
-            size_t wanted_num, size_t *translated_size, size_t *item_num
+static size_t IRAM_ATTR ws2811_rmt_encode(
+            rmt_encoder_t *base_encoder, rmt_channel_handle_t channel,
+            const void *data, size_t data_size, rmt_encode_state_t *ret_state
         ) {
-    if (src == NULL || dest == NULL) {
-        *translated_size = 0;
-        *item_num = 0;
-        return;
+    static const rmt_symbol_word_t reset_symbol = (rmt_symbol_word_t){
+        .duration0 = RESET_TICKS,
+        .level0 = 0,
+        .duration1 = 0,
+        .level1 = 0,
+    };
+    int state = 0;
+    rmt_encode_state_t substate = (rmt_encode_state_t)0;
+    size_t n_encoded = 0;
+    ws2811_rmt_encoder *encoder = (ws2811_rmt_encoder*)base_encoder;
+
+    if (!encoder->bytes_encoded) {
+        // Encode remaining bytes
+        n_encoded += encoder->bytes_encoder->encode(
+                encoder->bytes_encoder, channel,
+                data, data_size,
+                &substate
+            );
+
+        if (substate & RMT_ENCODING_COMPLETE) {
+            encoder->bytes_encoded = true;
+        }
     }
 
-    const uint32_t short_ticks = bit_ticks / 3;
-    const uint32_t long_ticks = bit_ticks - short_ticks;
-    const rmt_item32_t bit0 = {{{ short_ticks, 1, long_ticks, 0 }}}; // Logical 0
-    const rmt_item32_t bit1 = {{{ long_ticks, 1, short_ticks, 0 }}}; // Logical 1
-    size_t size = 0;
-    size_t num = 0;
-    uint8_t *psrc = (uint8_t *)src;
-    rmt_item32_t *pdest = dest;
-    while (size < src_size && num < wanted_num) {
-        for (int i = 0; i < 8; i++) {
-            // MSB first
-            if (*psrc & (1 << (7 - i))) {
-                pdest->val =  bit1.val;
-            } else {
-                pdest->val =  bit0.val;
-            }
-            num++;
-            pdest++;
+    if (encoder->bytes_encoded) {
+        // All bytes encoded; encode reset pulse
+        n_encoded += encoder->reset_encoder->encode(
+                encoder->reset_encoder, channel,
+                &reset_symbol, sizeof(reset_symbol),
+                &substate
+            );
+        if (substate & RMT_ENCODING_COMPLETE) {
+            state |= RMT_ENCODING_COMPLETE;
         }
-        size++;
-        psrc++;
     }
 
-    *translated_size = size;
-    *item_num = num;
-}
-
+    if (substate & RMT_ENCODING_MEM_FULL) {
+        state |= RMT_ENCODING_MEM_FULL;
+    }
 
-RMT_LEDs::RMT_LEDs(gpio_num_t _gpio, int length) :
-            LEDStrip(length), gpio(_gpio), channel(RMT_CHANNEL_MAX) {
-    rmt_config_t config = RMT_DEFAULT_CONFIG_TX(gpio, RMT_TX_CHANNEL);
-    // set counter clock to 40MHz
-    config.clk_div = 2;
+    *ret_state = (rmt_encode_state_t)state;
+    return n_encoded;
+}
 
-    ESP_ERROR_CHECK(rmt_config(&config));
-    channel = config.channel;
-    ESP_ERROR_CHECK(rmt_driver_install(channel, 0, 0));
+static esp_err_t ws2811_rmt_reset(rmt_encoder_t *base_encoder) {
+    ws2811_rmt_encoder *encoder = (ws2811_rmt_encoder*)base_encoder;
+    rmt_encoder_reset(encoder->bytes_encoder);
+    rmt_encoder_reset(encoder->reset_encoder);
+    encoder->bytes_encoded = false;
+    return ESP_OK;
+}
 
-    uint32_t counter_clk_hz = 0;
-    int err = rmt_get_counter_clock(channel, &counter_clk_hz);
-    if (err != ESP_OK) {
-        ESP_LOGE(TAG, "Failed to read RMT counter: %d", err);
-        return;
-    }
+static esp_err_t ws2811_rmt_del(rmt_encoder_t *base_encoder) {
+    ws2811_rmt_encoder *encoder = (ws2811_rmt_encoder*)base_encoder;
+    rmt_del_encoder(encoder->bytes_encoder);
+    rmt_del_encoder(encoder->reset_encoder);
+    return ESP_OK;
+}
 
-    rmt_translator_init(channel, ws2811_rmt_adapter);
+static bool IRAM_ATTR ws2811_tx_done(
+            rmt_channel_handle_t tx_chan,
+            const rmt_tx_done_event_data_t *edata,
+            void *user_ctx
+        ) {
+    BaseType_t high_task_wakeup = pdFALSE;
+    QueueHandle_t queue = (QueueHandle_t)user_ctx;
+    // send the transmitted RMT symbols to the parser task
+    xQueueSendFromISR(queue, edata, &high_task_wakeup);
+    return high_task_wakeup == pdTRUE;
+}
 
-    // ns -> ticks
-    bit_ticks = ((uint64_t)counter_clk_hz * WS2811_PULSE_WIDTH_NS) / 1e9;
 
-    ESP_LOGI(TAG, "Each bit is %d RMT ticks", bit_ticks);
+RMT_LEDs::RMT_LEDs(int _gpio, int length) :
+            LEDStrip(length), gpio(_gpio), channel(NULL),
+            encoder({{
+                        .encode = ws2811_rmt_encode,
+                        .reset = ws2811_rmt_reset,
+                        .del = ws2811_rmt_del,
+                    },
+                    NULL, NULL, false
+                }),
+            queue(xQueueCreate(1, sizeof(rmt_tx_done_event_data_t)))
+        {
+    rmt_tx_channel_config_t config = {
+        .gpio_num = gpio,                 // GPIO number
+        .clk_src = RMT_CLK_SRC_DEFAULT,   // select source clock
+        .resolution_hz = RMT_RESOLUTION_HZ, // 3.6 MHz tick resolution -> 278 ns/tick
+        .mem_block_symbols = 64,          // memory block size, 64 * 4 = 256Bytes
+        .trans_queue_depth = 1,           // set the number of transactions that can pend in the background
+        .flags = {
+            .invert_out = false,        // don't invert output signal
+            .with_dma = true,           // use DMA backend
+            .io_loop_back = 0,
+            .io_od_mode = 0,
+        },
+    };
+    ESP_ERROR_CHECK(rmt_new_tx_channel(&config, &channel));
+
+    rmt_tx_event_callbacks_t cbs = {
+        .on_trans_done = ws2811_tx_done,
+    };
+    ESP_ERROR_CHECK(rmt_tx_register_event_callbacks(channel, &cbs, queue));
+
+    ESP_ERROR_CHECK(rmt_enable(channel));
+
+    rmt_bytes_encoder_config_t bytes_config = {
+        .bit0 = {
+            .duration0 = SHORT_TICKS,
+            .level0 = 1,
+            .duration1 = LONG_TICKS,
+            .level1 = 0,
+        },
+        .bit1 = {
+            .duration0 = LONG_TICKS,
+            .level0 = 1,
+            .duration1 = SHORT_TICKS,
+            .level1 = 0,
+        },
+        .flags = {
+            .msb_first = 1,
+        },
+    };
+    ESP_ERROR_CHECK(rmt_new_bytes_encoder(&bytes_config, &encoder.bytes_encoder));
+
+    rmt_copy_encoder_config_t copy_config = {};
+    ESP_ERROR_CHECK(rmt_new_copy_encoder(&copy_config, &encoder.reset_encoder));
 
     configure(length);
 }
 
 RMT_LEDs::~RMT_LEDs() {
-    ESP_ERROR_CHECK(rmt_driver_uninstall(channel));
+    ESP_ERROR_CHECK(rmt_del_encoder(&encoder));
+    ESP_ERROR_CHECK(rmt_disable(channel));
+    ESP_ERROR_CHECK(rmt_del_channel(channel));
 }
 
 void RMT_LEDs::configure(int n_leds) {
-    // We don't own the RMT buffer
+    // We don't own the RMT buffer, but maybe we need a threadsafe copy of pixels?
 }
 
 void RMT_LEDs::show() {
     esp_err_t err;
+    static const rmt_transmit_config_t config = {
+        .loop_count = 0,
+        .flags = 0,
+    };
 
-    err = rmt_wait_tx_done(channel, 0);
-    if (err != ESP_OK) {
-        ESP_LOGE(TAG, "RMT TX incomplete: %d", err);
+    if (length <= 0) {
+        ESP_LOGW(TAG, "Invalid length write: %d", length);
         return;
     }
 
-    err = rmt_write_sample(channel, (uint8_t*)pixels, length * 3, false);
+    rmt_encoder_reset(&encoder);
+
+    err = rmt_transmit(channel, &encoder, pixels, length * 3, &config);
     if (err != ESP_OK) {
         ESP_LOGE(TAG, "Failed to write sample to RMT: %d", err);
+
+    } else {
+        // TODO: Do a queue check prior to TX instead
+        // This was an attempt to avoid clobbering pixel data,
+        // but that doesn't appear to be why everything gets weird during OTA.
+        rmt_tx_done_event_data_t tx_data;
+        if (xQueueReceive(queue, &tx_data, portMAX_DELAY) != pdTRUE) {
+            ESP_LOGE(TAG, "Failed to wait for last TX");
+        }
     }
 }

main/rmt_leds.hpp

@@ -1,20 +1,30 @@
 #pragma once
 
-#include <driver/rmt.h>
+#include <freertos/queue.h>
+
+#include <driver/rmt_tx.h>
 
 #include "leds.hpp"
 
 
+struct ws2811_rmt_encoder : rmt_encoder_t {
+    rmt_encoder_t *bytes_encoder;
+    rmt_encoder_t *reset_encoder;
+    bool bytes_encoded;
+};
+
 class RMT_LEDs : public LEDStrip {
 public:
-    RMT_LEDs(gpio_num_t gpio, int length = 0);
+    RMT_LEDs(int gpio, int length = 0);
     ~RMT_LEDs();
     void show();
     void length_changing(int len) { configure(len); }
 
 private:
-    gpio_num_t gpio;
-    rmt_channel_t channel;
+    int gpio;
+    rmt_channel_handle_t channel;
+    ws2811_rmt_encoder encoder;
+    QueueHandle_t queue;
 
     void configure(int length);
 };