Serial1.read() not functional

[AkhileshThorat]

Hardware:

Board: ESP32 Dev Module
Core Installation version: 1.0.1
IDE name: Arduino IDE
Flash Frequency: 40Mhz,DIO mode
PSRAM enabled: yes
Upload Speed: 921600
Computer OS: Windows 10

Description:

Trying to implement ModBusRTU on Serial1(rx=9,tx=10).Porting code from Atmega 2560 to ESP32 for Modbus protocol.Sending data successfully but fails to read data on the same serial port.

Sketch:

//Change the code below by your sketch
Minimal sketch as follows:

Serial1.begin(19200);//Initialisation

while(Serial1.available()) //reading Modbus response frame
  {
    mbresponse[retval++]=(char)Serial1.read();
  }
### Debug Messages:

[stickbreaker]

Pins 6-12 are used by flash memory. Can't be used by app.

[AkhileshThorat]

Pins 6-12 are used by flash memory. Can't be used by app.

I have used Dual Input Output(DIO) as flash mode,that makes pin 9 and 10 available for other .pins 9,10 are used by flash when QIO(Quad I/O) is enabled. I have used pins 9 and 10 in micropython for serial communication. this should work in arduino too, but I'm clueless whether it is about Hardware abstraction layer for arduino or some other stuff

[stickbreaker]

Did you physically disconnect the Flash from those lines?

[AkhileshThorat]

Did you physically disconnect the Flash from those lines?

No, I haven't.
Earlier I have tested code on a custom made Micropython (https://github.com/loboris/MicroPython_ESP32_psRAM_LoBo), without disconnecting flash from those serial lines,it works fine. but fails on Arduino

[nikisalli]

@AkhileshThorat any news on this? i'm having the same probem. it looks like the rx line beheaves as an output thus having low impedance. i tried manually setting it as an input but it didn't work

[AkhileshThorat]

@AkhileshThorat any news on this? i'm having the same probem. it looks like the rx line beheaves as an output thus having low impedance. i tried manually setting it as an input but it didn't work

@nikisalli Espressif recommends not to use pins 6 -11 for any other purpose/applications.
They're connected to SPI flash memory onboard and may result in guru meditation error if used. It's better you use other pins for your purpose, you can use any digital pin as serial(refer pin map of arduino-esp32).
If you're running out of GPIO's it's better to wait till new ESP32-S2 is available in market. It has Improved MCU functionalities and maybe some extra GPIO's for folks (who used external MCU for other purposes).

[nikisalli]

the problem is that i have a pcb with an uart module connected to pins 9 and 10 and i'd like to use it instead of ordering new pcbs :/

[AkhileshThorat]

the problem is that i have a pcb with an uart module connected to pins 9 and 10 and i'd like prefer to use it instead of ordering new pcbs :/

It's very uncertain that ESP32 won't throw error if you use 9,10 in a specific way. Serial works on 9 and 10 but only when used in very restrictive manner. like don't use it too often(keep atleast 15 seconds interval in between communication ). Always check for programming mode(it should be DIO and not QIO, QIO uses pin 9 and 10 for uploading code). Reset your ESP32 whenever you find your application is not running anymore.
Next time keep a habit of verifying functional behavior before making a PCB.

[nikisalli]

ok i'll make a new one then

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[AkhileshThorat]

There were many controversies surrounding using reserved IO pins , I think such pins should not be made accessible outside the module . Such pins should be kept inside the module only for memory interfacing or other interfaces.