[GitHub] [incubator-nuttx] vbenso commented on a diff in pull request #6992: WS2812 LED driver using ESP32's RMT peripheral

[GitBox <gi...@apache.org>]

vbenso commented on code in PR #6992:
URL: https://github.com/apache/incubator-nuttx/pull/6992#discussion_r961917770


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arch/xtensa/src/esp32/esp32_rmt.c:
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@@ -0,0 +1,315 @@
+/****************************************************************************
+ * arch/xtensa/src/esp32/esp32_rmt.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 <stdio.h>
+#include <sys/types.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <errno.h>
+#include <debug.h>
+
+#include <nuttx/kmalloc.h>
+#include <arch/board/board.h>
+#include <nuttx/irq.h>
+#include <nuttx/arch.h>
+
+#include "xtensa.h"
+
+#include "esp32_gpio.h"
+#include "esp32_rmt.h"
+#include "esp32_irq.h"
+#include "esp32_clockconfig.h"
+
+#include "hardware/esp32_dport.h"
+#include "hardware/esp32_gpio_sigmap.h"
+
+#ifdef CONFIG_ESP32_RMT
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Types
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+/* RMT methods */
+
+static void esp32rmt_reset(struct rmt_dev_s *dev);
+
+IRAM_ATTR static int esp32rmt_interrupt(int irq, void *context, void *arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: esp32rmt_reset
+ *
+ * Description:
+ *   Reset the RMT device.  Called early to initialize the hardware. This
+ *   function is called, before esp32_rmt_setup().
+ *
+ * Input Parameters:
+ *   dev - An instance of the "upper half" RMT driver state structure.
+ *
+ * Returned Value:
+ *  None
+ *
+ ****************************************************************************/
+
+static void esp32rmt_reset(struct rmt_dev_s *dev)
+{
+  irqstate_t flags;
+  int ret;
+  
+  flags = enter_critical_section();
+
+  modifyreg32(DPORT_PERIP_RST_EN_REG, DPORT_RMT_RST, 1);
+  modifyreg32(DPORT_PERIP_RST_EN_REG, DPORT_RMT_RST, 0);
+  putreg32(0xFFFFFFFF, RMT_INT_CLR_REG); /* Clear any spurious IRQ Flag */
+
+  leave_critical_section(flags);
+}
+
+/****************************************************************************
+ * Name: esp32rmt_setup
+ *
+ * Description:
+ *   Configure the RMT. This method is called the first time that the RMT
+ *   device is opened.  This will occur when the port is first opened.
+ *   This setup includes configuring and attaching RMT interrupts.
+ *
+ * Input Parameters:
+ *   dev - An instance of the "upper half" RMT driver state structure.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno on failure
+ *
+ ****************************************************************************/
+
+static int esp32rmt_setup(struct rmt_dev_s *dev)
+{
+  irqstate_t flags;
+  int ret = OK;
+
+  flags = enter_critical_section();
+
+  if (dev->cpuint != -ENOMEM)
+    {
+      /* Disable the provided CPU Interrupt to configure it. */
+      up_disable_irq(dev->cpuint);
+    }
+
+  dev->cpu = up_cpu_index();
+  dev->cpuint = esp32_setup_irq(dev->cpu, dev->periph,
+                                2, ESP32_CPUINT_LEVEL);
+  if (dev->cpuint < 0)
+    {
+      /* Failed to allocate a CPU interrupt of this type. */
+  
+      ret = dev->cpuint;
+      leave_critical_section(flags);
+  
+      return ret;
+    }
+  
+  ret = irq_attach(dev->irq, esp32rmt_interrupt, dev);
+  
+  if (ret != OK)
+    {
+      /* Failed to attach IRQ, so CPU interrupt must be freed. */
+  
+      esp32_teardown_irq(dev->cpu, dev->periph, dev->cpuint);
+      dev->cpuint = -ENOMEM;
+      leave_critical_section(flags);
+  
+      return ret;
+    }
+
+  /* Enable the CPU interrupt that is linked to the RMT device. */
+  up_enable_irq(dev->cpuint);
+
+  leave_critical_section(flags);
+
+  return ret;
+}
+
+/****************************************************************************
+ * Name: esp32rmt_interrupt
+ *
+ * Description:
+ *   RMT TX interrupt handler
+ *
+ * Input Parameters:
+ *   irq - The IRQ number of the interrupt.
+ *   context - The register state save array at the time of the interrupt.
+ *   arg - The pointer to driver structure.
+ *
+ * Returned Value:
+ *   Zero on success; a negated errno on failure
+ *
+ ****************************************************************************/
+IRAM_ATTR static int esp32rmt_interrupt(int irq, void *context, void *arg)
+{
+  struct rmt_dev_s *dev = (struct rmt_dev_s *)arg;
+  uint32_t regval = getreg32(RMT_INT_ST_REG);
+  uint32_t total_pixels;
+  uint32_t current_pixel;
+  uint32_t dst_mem;
+  uint32_t used_words;
+  uint8_t *pixel_ptr;
+  
+  if (regval & RMT_CHn_TX_END_INT_ST(dev->channel))
+    {
+      putreg32(RMT_CHn_TX_END_INT_CLR(dev->channel), RMT_INT_CLR_REG);
+      regval = getreg32(RMT_INT_ENA_REG);
+      regval &= ~(RMT_CHn_TX_END_INT_ENA(dev->channel));
+      putreg32(regval, RMT_INT_ENA_REG);
+      nxsem_post(&dev->tx_sem);
+    }
+  else if (regval & RMT_CHn_TX_THR_EVENT_INT_ST(dev->channel))
+    {
+      putreg32(RMT_CHn_TX_THR_EVENT_INT_CLR(dev->channel), RMT_INT_CLR_REG);
+      total_pixels = dev->data_len;
+      current_pixel = dev->next_pixel_to_load;
+      dst_mem = dev->start_address;
+      if(dev->frame++==1)
+        dst_mem += dev->reload_thresh * 4;
+      
+      if (dev->frame > 1)
+        dev->frame = 0;
+      
+      used_words = 0;
+      pixel_ptr = dev->data_ptr + current_pixel;
+  
+      while (used_words < dev->reload_thresh)
+        {
+          if (current_pixel < total_pixels)
+            {
+              register uint8_t pixel = (*pixel_ptr++);
+              for (register uint32_t i = 0; i < 8; i++)
+                {
+                  if (pixel & 0x80L)
+                    {
+                      putreg32(LOGIC_ONE, dst_mem);
+                    }
+                  else
+                    {
+                      putreg32(LOGIC_ZERO, dst_mem);
+                    }
+                  pixel <<= 1;
+                  dst_mem += 4;
+                }
+              used_words+=8;
+              current_pixel++;
+            }
+          else
+            {
+              regval = getreg32(RMT_INT_ENA_REG);
+              regval |= RMT_CHn_TX_END_INT_ENA(dev->channel);
+              putreg32(regval, RMT_INT_ENA_REG);
+              putreg32(0, dst_mem);
+              break;
+            }
+        }
+      
+      dev->next_pixel_to_load = current_pixel;
+    }
+  else
+    {
+      /* Perhaps an error, have no info on that */
+      putreg32(regval, RMT_INT_CLR_REG);
+    }
+  
+  return OK;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: esp32_rmtinitialize
+ *
+ * Description:
+ *   Initialize the selected RMT device
+ *
+ * Input Parameters:
+ *   output_pin - the pin used for output
+ *   channel    - the RMT's channel that will be used
+ *
+ * Returned Value:
+ *   Valid RMT device structure reference on success; a NULL on failure
+ *
+ ****************************************************************************/
+
+struct rmt_dev_s *esp32_rmtinitialize(int output_pin, int channel)
+{
+  struct rmt_dev_s *rmtdev;
+  irqstate_t flags;
+
+  flags = enter_critical_section();

Review Comment:
   Nice to know that. 
   I've used the TWAI as reference, will change it to the the spinlock approach that the SPI uses. 



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