Improves UART reading performance

Author: SuGlider

cores/esp32/HardwareSerial.cpp

@@ -450,10 +450,12 @@ int HardwareSerial::peek(void)
 
 int HardwareSerial::read(void)
 {
-    if(available()) {
-        return uartRead(_uart);
+    uint8_t c = 0;
+    if (uartReadBytes(_uart, &c, 1, 0) == 1) {
+        return c;
+    } else {
+        return -1;
     }
-    return -1;
 }
 
 // read characters into buffer
@@ -462,16 +464,7 @@ int HardwareSerial::read(void)
 // the buffer is NOT null terminated.
 size_t HardwareSerial::read(uint8_t *buffer, size_t size)
 {
-    size_t avail = available();
-    if (size < avail) {
-        avail = size;
-    }
-    size_t count = 0;
-    while(count < avail) {
-        *buffer++ = uartRead(_uart);
-        count++;
-    }
-    return count;
+    return uartReadBytes(_uart, buffer, size, 0);
 }
 
 void HardwareSerial::flush(void)

cores/esp32/esp32-hal-uart.c

@@ -326,6 +326,34 @@ uint32_t uartAvailableForWrite(uart_t* uart)
     return available;
 }
 
+size_t uartReadBytes(uart_t* uart, uint8_t *buffer, size_t size, uint32_t timeout_ms)
+{
+    if(uart == NULL || size == 0 || buffer == NULL) {
+        return 0;
+    }
+
+    size_t bytes_read = 0;
+
+    UART_MUTEX_LOCK();
+
+    if (uart->has_peek) {
+        uart->has_peek = false;
+        *buffer++ = uart->peek_byte;
+        size--;
+        bytes_read = 1;
+    }
+
+    if (size > 0) {
+       int len = uart_read_bytes(uart->num, buffer, size, pdMS_TO_TICKS(timeout_ms));
+       if (len < 0) len = 0;  // error reading UART
+       bytes_read += len;
+    }
+
+        
+    UART_MUTEX_UNLOCK();
+    return bytes_read;
+}
+
 
 uint8_t uartRead(uart_t* uart)
 {

cores/esp32/esp32-hal-uart.h

@@ -69,6 +69,7 @@ void uartGetEventQueue(uart_t* uart, QueueHandle_t *q);
 
 uint32_t uartAvailable(uart_t* uart);
 uint32_t uartAvailableForWrite(uart_t* uart);
+size_t uartReadBytes(uart_t* uart, uint8_t *buffer, size_t size, uint32_t timeout_ms);
 uint8_t uartRead(uart_t* uart);
 uint8_t uartPeek(uart_t* uart);