drivers/ws281x: add ESP32x hardware support

drivers/ws281x/Kconfig

@@ -26,6 +26,25 @@ config MODULE_WS281X_ESP32
     bool
     depends on HAS_ARCH_ESP32
 
+config MODULE_WS281X_ESP32_HW
+    bool "WS2812/SK6812 RGB LED uses ESP32x RMT"
+    depends on MODULE_WS281X_ESP32 && HAS_ESP_RMT
+    default y
+    help
+        The driver can use on ESP32x SoCs either the Remote Control (RMT)
+        peripheral or a bit-banging software implementation to generate the
+        RGB LED signal. Using the RMT peripheral requires more ROM and RAM but
+        does not use the CPU to generate the RGB LED signal. Disable this
+        option if saving ROM and RAM is required.
+
+config MODULE_WS281X_ESP32_SW
+    bool
+    depends on MODULE_WS281X_ESP32
+    default y if !MODULE_WS281X_ESP32_HW
+    help
+        Use the bit-banging software implementation to generate the RGB LED
+        signal.
+
 config HAVE_WS281X
     bool
     help

drivers/ws281x/Makefile.dep

@@ -15,3 +15,16 @@ endif
 ifneq (,$(filter ws281x_atmega,$(USEMODULE)))
   FEATURES_REQUIRED += cpu_core_atmega
 endif
+
+ifneq (,$(filter ws281x_esp32%,$(USEMODULE)))
+  FEATURES_REQUIRED += arch_esp32
+  ifneq (,$(filter ws281x_esp32_sw,$(USEMODULE)))
+    USEMODULE += ws281x_esp32
+  else
+    # use ESP32x RMT hardware implementation by default
+    FEATURES_REQUIRED += esp_rmt
+    USEMODULE += esp_idf_rmt
+    USEMODULE += ws281x_esp32
+    USEMODULE += ws281x_esp32_hw
+  endif
+endif

drivers/ws281x/esp32.c

@@ -1,5 +1,6 @@
 /*
  * Copyright 2020 Christian Friedrich Coors
+ *           2023 Gunar Schorcht
  *
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
@@ -15,6 +16,7 @@
  * @brief       Implementation of `ws281x_write_buffer()` for the ESP32x CPU
  *
  * @author      Christian Friedrich Coors <me@ccoors.de>
+ * @author      Gunar Schorcht <gunar@schorcht.net>
  *
  * @}
  */
@@ -23,21 +25,71 @@
 #include <stdint.h>
 #include <string.h>
 
+#include "board.h"
+#include "log.h"
+#include "periph_cpu.h"
+
 #include "ws281x.h"
 #include "ws281x_params.h"
 #include "ws281x_constants.h"
-#include "periph_cpu.h"
 
 #include "esp_private/esp_clk.h"
 #include "hal/cpu_hal.h"
 #include "soc/rtc.h"
 
+#ifdef MODULE_WS281X_ESP32_HW
+#include "esp_intr_alloc.h"
+#include "driver/rmt.h"
+#include "hal/rmt_types.h"
+#include "hal/rmt_ll.h"
+#include "soc/rmt_struct.h"
+#endif
+
 #define ENABLE_DEBUG 0
 #include "debug.h"
 
+#ifdef MODULE_WS281X_ESP32_HW
+
+static uint32_t _ws281x_one_on;
+static uint32_t _ws281x_one_off;
+static uint32_t _ws281x_zero_on;
+static uint32_t _ws281x_zero_off;
+
+static uint8_t _rmt_channel(ws281x_t *dev)
+{
+    for (unsigned i = 0; i < RMT_CH_NUMOF; i++) {
+        if (rmt_channel_config[i].gpio == dev->params.pin) {
+            return rmt_channel_config[i].channel;
+        }
+    }
+    assert(0);
+}
+#endif
+
 void ws281x_write_buffer(ws281x_t *dev, const void *buf, size_t size)
 {
     assert(dev);
+
+#ifdef MODULE_WS281X_ESP32_HW
+    /* determine used RMT channel from configured GPIO */
+    uint8_t channel = _rmt_channel(dev);
+
+    /* determine the current clock frequency */
+    uint32_t freq;
+    if (rmt_get_counter_clock(channel, &freq) != ESP_OK) {
+        LOG_ERROR("[ws281x_esp32] Could not get RMT counter clock\n");
+        return;
+    }
+
+    /* compute phase times used in ws2812_rmt_adapter once rmt_write_sample is called */
+    uint32_t total_cycles = freq / (NS_PER_SEC / WS281X_T_DATA_NS);
+    _ws281x_one_on = freq / (NS_PER_SEC / WS281X_T_DATA_ONE_NS);
+    _ws281x_one_off = total_cycles - _ws281x_one_on;
+    _ws281x_zero_on = freq / (NS_PER_SEC / WS281X_T_DATA_ZERO_NS);
+    _ws281x_zero_off = total_cycles - _ws281x_zero_on;
+
+    rmt_write_sample(channel, (const uint8_t *)buf, size, false);
+#else
     const uint8_t *pos = buf;
     const uint8_t *end = pos + size;
 
@@ -87,8 +139,45 @@ void ws281x_write_buffer(ws281x_t *dev, const void *buf, size_t size)
     /* final LOW phase */
     current_wait = cpu_hal_get_cycle_count();
     /* end of final LOW phase */
+#endif
 }
 
+#ifdef MODULE_WS281X_ESP32_HW
+static void IRAM_ATTR ws2812_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) {
+    if ((src == NULL) || (dest == NULL)) {
+        *translated_size = 0;
+        *item_num = 0;
+        return;
+    }
+
+    const rmt_item32_t bit0 = {{{ _ws281x_zero_on, 1, _ws281x_zero_off, 0 }}};
+    const rmt_item32_t bit1 = {{{ _ws281x_one_on, 1, _ws281x_one_off, 0 }}};
+
+    size_t size = 0;
+    size_t num = 0;
+    uint8_t *psrc = (uint8_t *)src;
+
+    while ((size < src_size) && (num < wanted_num)) {
+        uint8_t data = *psrc;
+        for (uint8_t cnt = 8; cnt > 0; cnt--) {
+            dest->val = (data & 0b10000000) ? bit1.val : bit0.val;
+            dest++;
+            num++;
+            data <<= 1;
+        }
+        size++;
+        psrc++;
+    }
+    *translated_size = size;
+    *item_num = num;
+}
+#endif
+
 int ws281x_init(ws281x_t *dev, const ws281x_params_t *params)
 {
     if (!dev || !params || !params->buf) {
@@ -98,9 +187,26 @@ int ws281x_init(ws281x_t *dev, const ws281x_params_t *params)
     memset(dev, 0, sizeof(ws281x_t));
     dev->params = *params;
 
+#ifdef MODULE_WS281X_ESP32_HW
+    static_assert(RMT_CH_NUMOF <= RMT_CH_NUMOF_MAX,
+                  "[ws281x_esp32] RMT configuration problem");
+
+    /* determine used RMT channel from configured GPIO */
+    uint8_t channel = _rmt_channel(dev);
+
+    rmt_config_t cfg = RMT_DEFAULT_CONFIG_TX(params->pin, channel);
+    cfg.clk_div = 2;
+
+    if ((rmt_config(&cfg) != ESP_OK) ||
+        (rmt_driver_install(channel, 0, 0) != ESP_OK) ||
+        (rmt_translator_init(channel, ws2812_rmt_adapter) != ESP_OK)) {
+        LOG_ERROR("[ws281x_esp32] RMT initialization failed\n");
+        return -EIO;
+    }
+#else
     if (gpio_init(dev->params.pin, GPIO_OUT)) {
         return -EIO;
     }
-
+#endif
     return 0;
 }