Forum Rule: Always post complete source code & details to reproduce any issue!
Results 1 to 3 of 3

Thread: Serial5 not work with ESP8266-01

  1. #1

    Serial5 not work with ESP8266-01

    The Serial5 (TX5 pin 33 and RX5 pin34) not work with module ESP8266-01.

    connexion from module ESP8266-01 is:

    ESP Teensy 3.6
    vcc vcc
    gnd gnd
    TX RX
    RX TX

    the code below not work

    void setup() { 
    void loop() {
      /* send everything received from the hardware uart to usb serial & vv */
      if (Serial.available() > 0) {
        char ch =;
      if (Serial5.available() > 0) {
        char ch =;
    the command AT display nothing on serial monitor

    i have tested to invert TX and RX and is a same

    i have tested with external power 3.3v for module ESP8266-01 and is a same.

    the module work well without teensy, with adapter usb-> serial using terminal a 115200 bauds.

    there is a problem with RX5 and TX5

    any idea ?

    thanks for your responses.
    Last edited by andromeda; 07-19-2019 at 12:26 AM.

  2. #2
    Problem resolved using shield for ESP8266-01.
    and connect TX from teensy to TX to shield and RX from teensy to RX to shield.

  3. #3
    Senior Member+ defragster's Avatar
    Join Date
    Feb 2015
    <edit> - crosspost ... congratualtions ... would have suggested that but read ... "i have tested to invert TX and RX and is a same" as saying that was already tried.

    Assuming the VCC voltages are right for both devices?

    I'd try shorting/crossing the T_3.6 Rx to Tx on Serial5 and make sure the port is properly configured and functional. Seems that sketch should just end up with Serial USB input going out Serial5 and then right back in Serial5 and back to Serial USB.

    Maybe do the same on the ESP to verify it is working.

    AFAIK all those pins should show 3 to 3.3V at rest when the ports are active after .begin().

    Once working changing those 'if ( .available() )' to 'while ( .available() )' will get the transfer done with less time wasted re-entering loop().

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts