Improves UART reading performance (espressif#7525)

* Improves UART reading performance

* overrides Stream::readBytes()

* fixes override signature

* adds some IDF error return  conditions

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 +464,13 @@ 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);
+}
+
+// Overrides Stream::readBytes() to be faster using IDF
+size_t HardwareSerial::readBytes(uint8_t *buffer, size_t length)
+{
+    return uartReadBytes(_uart, buffer, length, (uint32_t)getTimeout());
 }
 
 void HardwareSerial::flush(void)

cores/esp32/HardwareSerial.h

@@ -118,6 +118,12 @@ class HardwareSerial: public Stream
     {
         return read((uint8_t*) buffer, size);
     }
+    // Overrides Stream::readBytes() to be faster using IDF
+    size_t readBytes(uint8_t *buffer, size_t length);
+    size_t readBytes(char *buffer, size_t length)
+    {
+        return readBytes((uint8_t *) buffer, length);
+    }    
     void flush(void);
     void flush( bool txOnly);
     size_t write(uint8_t);

cores/esp32/esp32-hal-uart.c

@@ -331,7 +331,36 @@ 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;
+}
+
+// DEPRICATED but the original code will be kepts here as future reference when a final solution
+// to the UART driver is defined in the use case of reading byte by byte from UART.
 uint8_t uartRead(uart_t* uart)
 {
     if(uart == NULL) {
@@ -347,14 +376,15 @@ uint8_t uartRead(uart_t* uart)
     } else {
 
         int len = uart_read_bytes(uart->num, &c, 1, 20 / portTICK_RATE_MS);
-        if (len == 0) {
+        if (len <= 0) { // includes negative return from IDF in case of error
             c  = 0;
         }
     }
     UART_MUTEX_UNLOCK();
     return c;
 }
 
+
 uint8_t uartPeek(uart_t* uart)
 {
     if(uart == NULL) {
@@ -368,7 +398,7 @@ uint8_t uartPeek(uart_t* uart)
       c = uart->peek_byte;
     } else {
         int len = uart_read_bytes(uart->num, &c, 1, 20 / portTICK_RATE_MS);
-        if (len == 0) {
+        if (len <= 0) { // includes negative return from IDF in case of error
             c  = 0;
         } else {
             uart->has_peek = true;

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);