Adds RMT End of Transmission Level API (espressif#9238)

* RMT (featt):  adds a new function to set EOT level after RMT writing

* RMT (feat): adds new feature to set the EOT level after writing RMT channel

* adds return value to rmtSetEOT()

* adds bool return to rmtSetEOT()

* adds return value to the rmtSetEOT() function

* FIX (rmt): fixes eot_level setting using flags in the TX structure

* RMT(feat): Create RMT_EndOfTransmissionState.ino example

* Update cores/esp32/esp32-hal-rmt.h

Co-authored-by: Jan Procházka <90197375+P-R-O-C-H-Y@users.noreply.github.com>

* Update cores/esp32/esp32-hal-rmt.c

Co-authored-by: Jan Procházka <90197375+P-R-O-C-H-Y@users.noreply.github.com>

* Update cores/esp32/esp32-hal-rmt.c

Co-authored-by: Jan Procházka <90197375+P-R-O-C-H-Y@users.noreply.github.com>

---------

Co-authored-by: Jan Procházka <90197375+P-R-O-C-H-Y@users.noreply.github.com>

Author: SuGlider

cores/esp32/esp32-hal-rmt.c

@@ -61,6 +61,7 @@ struct rmt_obj_s {
   bool rmt_ch_is_looping;                    // Is this RMT TX Channel in LOOPING MODE?
   size_t *num_symbols_read;                  // Pointer to the number of RMT symbol read by IDF RMT RX Done
   uint32_t frequency_Hz;                     // RMT Frequency
+  uint8_t rmt_EOT_Level;                     // RMT End of Transmission Level - default is LOW
 
 #if !CONFIG_DISABLE_HAL_LOCKS
   SemaphoreHandle_t g_rmt_objlocks;           // Channel Semaphore Lock
@@ -185,6 +186,20 @@ static bool _rmtDetachBus(void *busptr)
    Public method definitions
 */
 
+bool rmtSetEOT(int pin, uint8_t EOT_Level)
+{
+  rmt_bus_handle_t bus = _rmtGetBus(pin, __FUNCTION__);
+  if (bus == NULL) {
+    return false;
+  }
+  if (!_rmtCheckDirection(pin, RMT_TX_MODE, __FUNCTION__)) {
+    return false;
+  }
+
+  bus->rmt_EOT_Level = EOT_Level > 0 ? 1 : 0;
+  return true;
+}
+
 bool rmtSetCarrier(int pin, bool carrier_en, bool carrier_level, uint32_t frequency_Hz, float duty_percent)
 {
   rmt_bus_handle_t bus = _rmtGetBus(pin, __FUNCTION__);
@@ -316,6 +331,10 @@ static bool _rmtWrite(int pin, rmt_data_t* data, size_t num_rmt_symbols, bool bl
     rmt_enable(bus->rmt_channel_h);
     bus->rmt_ch_is_looping = false;  // not looping anymore
   }
+  // sets the End of Transmission level to HIGH if the user has requested so
+  if (bus->rmt_EOT_Level) {
+    transmit_cfg.flags.eot_level = 1;  // EOT is HIGH
+  }
   if (loopCancel) {
     // just resets and releases the channel, maybe, already done above, then exits
     bus->rmt_ch_is_looping = false;
@@ -487,7 +506,7 @@ bool rmtInit(int pin, rmt_ch_dir_t channel_direction, rmt_reserve_memsize_t mem_
   // store the RMT Freq to check Filter and Idle valid values in the RMT API
   bus->frequency_Hz = frequency_Hz;
   // pulses with width smaller than min_ns will be ignored (as a glitch)
-  bus->signal_range_min_ns = 0; // disabled
+  //bus->signal_range_min_ns = 0; // disabled  --> not necessary CALLOC set all to ZERO.
   // RMT stops reading if the input stays idle for longer than max_ns
   bus->signal_range_max_ns = (1000000000 / frequency_Hz) * RMT_LL_MAX_IDLE_VALUE; // maximum possible
   // creates the event group to control read_done and write_done

cores/esp32/esp32-hal-rmt.h

@@ -76,6 +76,20 @@ typedef union {
 */
 bool rmtInit(int pin, rmt_ch_dir_t channel_direction, rmt_reserve_memsize_t memsize, uint32_t frequency_Hz);
 
+/**
+     Sets the End of Transmission level to be set for the <pin> when the RMT transmission ends.
+     This function affects how rmtWrite(), rmtWriteAsync() or rmtWriteLooping() will set the pin after writing the data.
+     The default EOT level is LOW, in case this function isn't used before RMT Writing.
+     This level can be set for each RMT pin and can be changed between writings to the same pin.
+
+     <EOT_Level> shall be Zero (LOW) or non-zero (HIGH) value.
+     It only affects the transmission process, therefore, it doesn't affect any IDLE LEVEL before starting the RMT transmission. 
+     The pre-transmission idle level can be set manually calling, for instance, digitalWrite(pin, Level).
+
+     Returns <true> when EOT has been correctly set for <pin>, <false> otherwise.
+*/
+bool rmtSetEOT(int pin, uint8_t EOT_Level);
+
 /**
      Sending data in Blocking Mode. 
      <rmt_symbol> is a 32 bits structure as defined by rmt_data_t type.

libraries/ESP32/examples/RMT/RMT_EndOfTransmissionState/RMT_EndOfTransmissionState.ino

@@ -0,0 +1,59 @@
+#define BLINK_GPIO 2
+#define EOT_INITIAL_STATE_TIME_MS 1000
+
+// BLINK_GPIO shall start at RMT_EOT (HIGH or LOW) as initial state for EOT_INITIAL_STATE_TIME_MS, 
+// BLINK: 1 second ON, 1 second OFF and then return/stay to RMT_EOT level at the end.
+#define RMT_EOT HIGH
+
+// RMT is at 400KHz with a 2.5us tick
+// This RMT data sends a 0.5Hz pulse with 1s High and 1s Low signal
+rmt_data_t blink_1s_rmt_data[] = {
+  // 400,000 x 2.5us = 1 second ON
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  {25000, 1, 25000, 1,},
+  // 400,000 x 2.5us = 1 second OFF
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  {25000, 0, 25000, 0,},
+  // Looping mode needs a Zero ending data to mark the EOF
+  {0, 0, 0, 0}
+};
+
+void setup() {
+  Serial.begin(115200);
+  Serial.println("Starting Blink testing...");
+  Serial.flush();
+  
+  // 1 RMT Block has 64 RMT_SYMBOLS (ESP32|ESP32S2) or 48 RMT_SYMBOLS (ESP32C3|ESP32S3)
+  if (!rmtInit(BLINK_GPIO, RMT_TX_MODE, RMT_MEM_NUM_BLOCKS_1, 400000)) { //2.5us tick
+    Serial.println("===> rmtInit Error!");
+  }
+   
+  // sets the End of Transmission Level to HIGH, after writing to the pin. DEFAULT is LOW.
+  rmtSetEOT(BLINK_GPIO, RMT_EOT);
+  // set initial RMT state by writing a single RMT data
+  rmt_data_t initStateSetup_rmt_data[] = { {1, RMT_EOT, 0, 0} };  
+  rmtWrite(BLINK_GPIO, initStateSetup_rmt_data, RMT_SYMBOLS_OF(initStateSetup_rmt_data), RMT_WAIT_FOR_EVER);
+  Serial.printf("\nLED GPIO%d start in the inital level %s\n", BLINK_GPIO, RMT_EOT == LOW ? "LOW" : "HIGH");
+  delay(EOT_INITIAL_STATE_TIME_MS); // set initial state of the LED is set by RMT_EOT.
+   
+  // Send the data and wait until it is done - set EOT level to HIGH
+  Serial.printf("\nLED GPIO%d Blinks 1 second HIGH - 1 second LOW.\n", BLINK_GPIO);
+  if (!rmtWrite(BLINK_GPIO, blink_1s_rmt_data, RMT_SYMBOLS_OF(blink_1s_rmt_data) - 2, RMT_WAIT_FOR_EVER)) {
+    Serial.println("===> rmtWrite Blink 1s Error!");
+  }
+  Serial.printf("\nLED GPIO%d goes to the EOT level %s\n", BLINK_GPIO, RMT_EOT == LOW ? "LOW" : "HIGH");
+}
+
+void loop(){}