From 10b9474c28247d1f9382f03fe340783430aef3ff Mon Sep 17 00:00:00 2001
From: Tobias Blum <tblum@outlook.com>
Date: Sat, 18 Jan 2020 23:51:46 +0100
Subject: [PATCH] Eliminate flickering by using ESP32_RMT library

---
 src/ESP32_RMT_Driver.h | 71 ++++++++++++++++++++++++++++++++++++++++++
 src/main.cpp           | 11 +++++++
 2 files changed, 82 insertions(+)
 create mode 100644 src/ESP32_RMT_Driver.h

diff --git a/src/ESP32_RMT_Driver.h b/src/ESP32_RMT_Driver.h
new file mode 100644
index 0000000..552318c
--- /dev/null
+++ b/src/ESP32_RMT_Driver.h
@@ -0,0 +1,71 @@
+#include "driver/rmt.h"
+
+#define APB_CLK_MHZ 80 // default RMT CLK source (80MHz)
+#define RMT_CLK_DIV  2 // RMT CLK divider
+#define RMT_TICK (RMT_CLK_DIV * 1000 / APB_CLK_MHZ) // 25ns
+
+// timing parameters for WS2812B LEDs. you may need to
+// tweek these if you're using a different kind of LED
+#define T1_TICKS      250 / RMT_TICK // 250ns
+#define T2_TICKS      625 / RMT_TICK // 625ns
+#define T3_TICKS      375 / RMT_TICK // 375ns
+#define RESET_TICKS 50000 / RMT_TICK // 50us
+
+/*
+ * Convert uint8_t type of data to rmt format data.
+ */
+static void IRAM_ATTR u8_to_rmt(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  = {{{ T1_TICKS,            1, T2_TICKS + T3_TICKS, 0 }}}; //Logical 0
+    const rmt_item32_t bit1  = {{{ T1_TICKS + T2_TICKS, 1, T3_TICKS           , 0 }}}; //Logical 1
+    const rmt_item32_t reset = {{{ RESET_TICKS/2      , 0, RESET_TICKS/2      , 0 }}}; //Reset
+    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) {
+      if(size < src_size - 1) { // have more pixel data, so translate into RMT items
+        (pdest++)->val =  (*psrc & B10000000) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B01000000) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00100000) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00010000) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00001000) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00000100) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00000010) ? bit1.val : bit0.val;
+        (pdest++)->val =  (*psrc & B00000001) ? bit1.val : bit0.val;
+        num += 8;
+      } else { // no more pixel data, last RMT item is the reset pulse
+        (pdest++)->val =  reset.val;
+        num++;
+      }
+      size++;
+      psrc++;
+    }
+    *translated_size = size;
+    *item_num = num;
+}
+
+/*
+ * Initialize the RMT Tx channel
+ */
+static void rmt_tx_int(rmt_channel_t channel, uint8_t gpio) {
+    rmt_config_t config;
+    config.rmt_mode = RMT_MODE_TX;
+    config.channel = channel;
+    config.gpio_num = gpio_num_t(gpio);
+    config.clk_div = RMT_CLK_DIV;
+    config.mem_block_num = 1; // 64 pulse "items" per block
+    config.tx_config.loop_en = 0;
+    config.tx_config.carrier_en = 0;
+    config.tx_config.idle_output_en = 1;
+    config.tx_config.idle_level = RMT_IDLE_LEVEL_LOW;
+
+    rmt_config(&config);
+    rmt_driver_install(config.channel, 0, 0);
+    rmt_translator_init(config.channel, u8_to_rmt);
+}
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index f9be8cf..6bd9d5c 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -37,6 +37,7 @@
 #include <WS2812FX.h>
 #include "FS.h"
 #include "SPIFFS.h"
+#include "ESP32_RMT_Driver.h"
 
 
 // CA certificate for login.microsoftonline.com
@@ -484,6 +485,14 @@ void neopixelTask(void * parameter) {
 	}
 }
 
+void customShow(void) {
+  uint8_t *pixels = ws2812fx.getPixels();
+  // numBytes is one more then the size of the ws2812fx's *pixels array.
+  // the extra byte is used by the driver to insert the LED reset pulse at the end.
+  uint16_t numBytes = ws2812fx.getNumBytes() + 1;
+  rmt_write_sample(RMT_CHANNEL_0, pixels, numBytes, false); // channel 0
+}
+
 
 /**
  * Main functions
@@ -497,6 +506,7 @@ void setup()
 
 	// WS2812FX
 	ws2812fx.init();
+	rmt_tx_int(RMT_CHANNEL_0, ws2812fx.getPin());
 	ws2812fx.start();
 	setAnimation(0, FX_MODE_STATIC, WHITE);
 
@@ -517,6 +527,7 @@ void setup()
 
 	// WS2812FX
 	ws2812fx.setLength(atoi(paramNumLedsValue));
+	ws2812fx.setCustomShow(customShow);
 
 	// HTTP server - Set up required URL handlers on the web server.
 	server.on("/", handleRoot);