Example for controlling a chain of WS2812 LEDs using ESP32 RMT periph…

examples/ws2812esp32rmt/Kconfig

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+#
+# For a description of the syntax of this configuration file,
+# see the file kconfig-language.txt in the NuttX tools repository.
+#
+
+config EXAMPLES_WS2812_ESP32_RMT
+	tristate "ws2812 Demo Program using ESP32_RMT"
+	depends on ESP32_RMT
+	default n
+	---help---
+		Enable the ws2812 demo, using ESP32 RMT peripheral to generate the pulses
+
+if EXAMPLES_WS2812_ESP32_RMT
+
+config EXAMPLES_WS2812_ESP32_RMT_PRIORITY
+	int "Task Priority"
+	default 100
+
+config EXAMPLES_WS2812_ESP32_RMT_STACKSIZE
+	int "Stack Size"
+	default DEFAULT_TASK_STACKSIZE
+
+endif

examples/ws2812esp32rmt/Make.defs

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+############################################################################
+# apps/examples/ws2812/Make.defs
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+ifneq ($(CONFIG_EXAMPLES_WS2812_ESP32_RMT),)
+CONFIGURED_APPS += $(APPDIR)/examples/ws2812esp32rmt
+endif

examples/ws2812esp32rmt/Makefile

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+############################################################################
+# apps/examples/ws2812/Makefile
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.  The
+# ASF licenses this file to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance with the
+# License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+# License for the specific language governing permissions and limitations
+# under the License.
+#
+############################################################################
+
+include $(APPDIR)/Make.defs
+
+# MTD R/W buffer test Example
+
+PROGNAME = ws2812esp32rmt
+PRIORITY = $(CONFIG_EXAMPLES_WS2812_ESP32_RMT_PRIORITY)
+STACKSIZE = $(CONFIG_EXAMPLES_WS2812_ESP32_RMT_STACKSIZE)
+MODULE = $(CONFIG_EXAMPLES_WS2812_ESP32_RMT)
+
+MAINSRC = ws2812esp32rmt_main.c
+
+include $(APPDIR)/Application.mk

examples/ws2812esp32rmt/ws2812esp32rmt_main.c

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+/****************************************************************************
+ * apps/examples/ws2812esp32rmt/ws2812esp32rmt_main.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <debug.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define APB_PERIOD (12.5)
+
+#define T0H ((uint16_t)(350 / APB_PERIOD))   // ns
+#define T0L ((uint16_t)(900 / APB_PERIOD))   // ns
+#define T1H ((uint16_t)(900 / APB_PERIOD))   // ns
+#define T1L ((uint16_t)(350 / APB_PERIOD))   // ns
+#define RES ((uint16_t)(60000 / APB_PERIOD)) // ns
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+struct led_s
+  {
+    uint8_t r;
+    uint8_t g;
+    uint8_t b;
+  };
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static int fd;
+static uint32_t *rmt_buffer;
+static uint32_t rmt_buffer_len_in_words;
+static uint32_t leds_buffer_len_in_bytes;
+static struct led_s *leds_buffer;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+static uint32_t map_byte_to_words(uint8_t byte, uint32_t *dst)
+{
+  uint32_t ret = 0;
+  uint8_t mask = 0x80;
+  for (int i = 0; i < 8; i++)
+    {
+      uint8_t bit = byte&mask;
+      mask >>= 1;
+      uint32_t word;
+      if (bit)
+        {
+          word = (T1L << 16) | (0x8000 | T1H);
+        }
+        else
+        {
+          word = (T0L << 16) | (0x8000 | T0H);
+        }
+
+      *dst = word;
+      dst++;
+      ret++;
+    }
+
+  return ret;
+}
+
+static int map_leds_to_words(struct led_s *leds,
+            uint32_t n_leds,
+            uint32_t *dst,
+            uint32_t dst_len_in_words
+          )
+{
+  int ret = OK;
+
+  if (!dst || !leds)
+    {
+      return -1;
+    }
+
+  uint32_t required_words = n_leds * 3 * 8;
+
+  if (required_words >= dst_len_in_words)
+    {
+      _err("Required %d words, but buffer has only:%d",
+        required_words, dst_len_in_words
+      );
+      return -1;
+    }
+
+  uint32_t dst_offset = 0;
+  for (uint32_t led_idx = 0; led_idx < n_leds; led_idx++)
+    {
+      dst_offset += map_byte_to_words(leds[led_idx].g, dst + dst_offset);
+      dst_offset += map_byte_to_words(leds[led_idx].r, dst + dst_offset);
+      dst_offset += map_byte_to_words(leds[led_idx].b, dst + dst_offset);
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * ws2812esp32rmt_main
+ ****************************************************************************/
+
+int main(int argc, FAR char *argv[])
+{
+  if (argc < 2)
+    {
+      printf("usage: %s channel led_count\n", argv[0]);
+      exit(1);
+    }
+
+  int ch_idx = atoi(argv[1]);
+  if (ch_idx >= 8)
+    {
+      printf("channel must be int the range 0~7\n");
+      exit(1);
+    }
+
+  uint32_t n_leds = atoi(argv[2]);
+
+  char dev_name[50];
+  snprintf(dev_name, 50, "/dev/rmt%d", ch_idx);
+  fd = open(dev_name, O_WRONLY);
+  if (fd < 0)
+    {
+      fprintf(stderr,
+              "ws2812esp32rmt: open %s failed: %d\n",
+              dev_name,
+              errno);
+      goto errout_with_dev;
+    }
+
+  _info("size of (struct led_s) is:%d", sizeof(struct led_s));
+
+  leds_buffer_len_in_bytes = sizeof(struct led_s)*n_leds;
+  leds_buffer = (struct led_s *)malloc(leds_buffer_len_in_bytes);
+  _info("leds:%d - leds_buffer %p len:%d\n",
+    n_leds,
+    leds_buffer,
+    leds_buffer_len_in_bytes
+  );
+
+  if (!leds_buffer)
+    {
+      _err("failure allocating %d bytes for LED buffer",
+        leds_buffer_len_in_bytes
+      );
+      goto errout;
+    }
+
+  rmt_buffer_len_in_words = (leds_buffer_len_in_bytes * 8 + 1);
+  rmt_buffer = (uint32_t *)malloc(rmt_buffer_len_in_words * 4);
+  _info("words:%d - rmt_buffer %p rmt_buffer_len_in_words:%d\n",
+    rmt_buffer_len_in_words,
+    rmt_buffer,
+    rmt_buffer_len_in_words
+  );
+
+  if (!rmt_buffer)
+    {
+      _err("failure allocating %d words for RMT word buffer",
+        rmt_buffer_len_in_words
+      );
+      goto errout;
+    }
+
+  int pos = 0;
+  int direction = 0;
+
+  /* Run the display loop */
+
+  while (1)
+    {
+      int n_loops = 30;
+      for (int i = 0; i < n_loops; ++i)
+        {
+          for (int l = 0; l < n_leds; l++)
+            {
+              if (!direction)
+                leds_buffer[l].r = i;
+              else
+                leds_buffer[l].r = 30 - i;
+
+              leds_buffer[l].g = 0x00;
+              leds_buffer[l].b = 0x00;
+
+              if (l == pos)
+                {
+                  leds_buffer[l].r = 0x00;
+                  leds_buffer[l].g = 0xff;
+                  leds_buffer[l].b = 0x00;
+                }
+            }
+
+          if (pos++ >= n_leds)
+              pos = 0;
+          int ret;
+          ret = map_leds_to_words(leds_buffer,
+            n_leds,
+            rmt_buffer,
+            rmt_buffer_len_in_words
+          );
+
+          if (ret)
+            {
+              _err("error mapping leds to words");
+              goto errout;
+            }
+
+          ret = write(fd, rmt_buffer, rmt_buffer_len_in_words * 4);
+
+          if (ret < 0)
+            {
+              _err("error writing to device, %d errno:%d", ret, errno);
+              goto errout_with_dev;
+            }
+
+/****************************************************************************
+ * Must sleep so the WS2812 can understand the EOT
+ ****************************************************************************/
+
+          usleep(50000);
+        }
+
+      direction = !direction;
+    }
+
+  free(leds_buffer);
+  free(rmt_buffer);
+  close(fd);
+  fflush(stdout);
+  return OK;
+
+errout_with_dev:
+  close(fd);
+
+errout:
+  fflush(stdout);
+  return ERROR;
+}