From ed220bd0420236e9ff95888f7459f0eb9c97a570 Mon Sep 17 00:00:00 2001
From: hreintke <hreintke@tauri.nl>
Date: Sun, 26 Jan 2020 23:38:06 +0100
Subject: [PATCH] Minimize HardwareSerial Receive and Transmit delays (#3664)

* Minimize HardwareSerial Receive and Transmit delays

* Remove uartRxFifoToQueue from esp-hal-uart.h

Co-authored-by: Me No Dev <me-no-dev@users.noreply.github.com>
---
 cores/esp32/esp32-hal-uart.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/cores/esp32/esp32-hal-uart.c b/cores/esp32/esp32-hal-uart.c
index 90acf54f..8ec1fe6f 100644
--- a/cores/esp32/esp32-hal-uart.c
+++ b/cores/esp32/esp32-hal-uart.c
@@ -208,6 +208,11 @@ uart_t* uartBegin(uint8_t uart_nr, uint32_t baudrate, uint32_t config, int8_t rx
         uart->dev->conf0.stop_bit_num = ONE_STOP_BITS_CONF;
         uart->dev->rs485_conf.dl1_en = 1;
     }
+
+    // tx_idle_num : idle interval after tx FIFO is empty(unit: the time it takes to send one bit under current baudrate)
+    // Setting it to 0 prevents line idle time/delays when sending messages with small intervals
+    uart->dev->idle_conf.tx_idle_num = 0;  //
+
     UART_MUTEX_UNLOCK();
 
     if(rxPin != -1) {
@@ -265,7 +270,7 @@ uint32_t uartAvailable(uart_t* uart)
     if(uart == NULL || uart->queue == NULL) {
         return 0;
     }
-    return uxQueueMessagesWaiting(uart->queue);
+    return (uxQueueMessagesWaiting(uart->queue) + uart->dev->status.rxfifo_cnt) ;
 }
 
 uint32_t uartAvailableForWrite(uart_t* uart)
@@ -276,12 +281,27 @@ uint32_t uartAvailableForWrite(uart_t* uart)
     return 0x7f - uart->dev->status.txfifo_cnt;
 }
 
+void uartRxFifoToQueue(uart_t* uart)
+{
+	uint8_t c;
+    UART_MUTEX_LOCK();
+    while(uart->dev->status.rxfifo_cnt || (uart->dev->mem_rx_status.wr_addr != uart->dev->mem_rx_status.rd_addr)) {
+        c = uart->dev->fifo.rw_byte;
+        xQueueSend(uart->queue, &c, 0);
+    }
+    UART_MUTEX_UNLOCK();
+}
+
 uint8_t uartRead(uart_t* uart)
 {
     if(uart == NULL || uart->queue == NULL) {
         return 0;
     }
     uint8_t c;
+    if ((uxQueueMessagesWaiting(uart->queue) == 0) && (uart->dev->status.rxfifo_cnt > 0))
+    {
+    	uartRxFifoToQueue(uart);
+    }
     if(xQueueReceive(uart->queue, &c, 0)) {
         return c;
     }
@@ -294,6 +314,10 @@ uint8_t uartPeek(uart_t* uart)
         return 0;
     }
     uint8_t c;
+    if ((uxQueueMessagesWaiting(uart->queue) == 0) && (uart->dev->status.rxfifo_cnt > 0))
+    {
+    	uartRxFifoToQueue(uart);
+    }
     if(xQueuePeek(uart->queue, &c, 0)) {
         return c;
     }