Doubt - uart usage

phfbertoleti · August 14, 2019, 2:17am

Hi there!

I have some doubts regarding usage of tx and rx of uart0. Please, would anyone help me?

Here is the doubt: I need to use an uart to communicate heltec wifi lora v2 module to an external board. Considering heltec lora wifi v2 schematic, uart 0 is the uart wired to tx and rx in pin headers (identified as tx and rx). However, usb / uart converter cp2102 uses uart 0 too (to communicate a pc with the board and write firmware to esp32).
As uart 0 is the only uart available to user in this module (uart 1 is for flash and uart 2 pins are being user to another module features), can I use uart 0 WITHOUT taking risk of cannot write firmware to esp32 no more (I mean, use uart 0 and don’t make the esp32 unflashable again)? If yes, how can I do that?

Thanks in advance.

Supporter · August 14, 2019, 5:08am

Hello @phfbertoleti

I don’t think the UART0 is the only available UART for users.

ESP32 have IO_MUX function, any GPIO can be configured to a UART pin, I2C pin, SPI pin, etc.

Here is the example code of how to config UART1 and UART2:

github.com

HelTecAutomation/Heltec_ESP32/blob/master/examples/ESP32/Serial2/Serial2.ino

/*
 * Heltec Automation ESP32 Serial 2 example.
 * work with ESP32's IO MUX
*/

//HardwareSerial Serial2(2);

void setup() {

  Serial.begin(115200);

  // Serial2.begin(unsigned long baud, uint32_t config, int8_t rxPin, int8_t txPin, bool invert)
  // The txPin & rxPin can set to any output pin
  Serial2.begin(115200, SERIAL_8N1, 18, 17);
}

void loop() {

  if(Serial.available()) {
    int ch = Serial.read();

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phfbertoleti · August 14, 2019, 2:28pm

Nice!

@Supporter, thanks for the information.