ESP32-S3 UART Issue on IO19 & IO20 – Data Corruption

[mightChamp]

Board

ESP32-S3

Device Description

esp32-s3 wroom 1 Module

Hardware Configuration

IO19 and IO20 as Uart RX and TX respectively

Version

v3.2.0

IDE Name

Arduino IDE

Operating System

Windows 11

Flash frequency

40Mhz

PSRAM enabled

no

Upload speed

921600

Description

We are attempting to use IO19 and IO20 as UART pins (115200 baud rate) but are encountering unexpected issues. While UART communication works flawlessly on IO17 and IO18 with no data corruption, switching to IO19 and IO20 results in byte corruption.

please clarify the following:

1. Can GPIO19 and GPIO20 (USB pins) be reliably used for UART communication, as well as for general input and output?

2. Are there any specific software configurations or additional code modifications required to enable proper UART functionality on these pins?

Sketch

void setup(){
Serial.begin(115200);
Serial1.begin(115200,SERIAL_8N1,19,20);
}

void loop(){
while(Serial.available())Serial1.write(Serial.read());
while(Serial1.available())Serial.write(Serial1.read());
}

Debug Message

Not useful logs, as corrupted data bytes only.

Other Steps to Reproduce

No response

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[SuGlider]

@mightChamp - Does it enable USB CDC when buiding the test example?

[mightChamp]

No, I didn't Enable USB CDC when building the test example.

[smartes]

Have you tried gpio_dump_io_configuration()

Below is an example of how to dump the configuration of GPIO4, GPIO18, and GPIO26:
gpio_dump_io_configuration(stdout, (1ULL << 4) | (1ULL << 18) | (1ULL << 26));

And later on the page
Configure USB PHY Pins to GPIO

gpio_config_t usb_phy_conf = {
    .pin_bit_mask = (1ULL << USB_PHY_DP_PIN) | (1ULL << USB_PHY_DM_PIN),
    .mode = GPIO_MODE_INPUT_OUTPUT,
    .pull_up_en = 0,
    .pull_down_en = 0,
    .intr_type = GPIO_INTR_DISABLE,
};
gpio_config(&usb_phy_conf);

[SuGlider]

@mightChamp - some answers:

Can GPIO19 and GPIO20 (USB pins) be reliably used for UART communication, as well as for general input and output?

Yes, it can be used for any compatible purpose and peripheral.

Are there any specific software configurations or additional code modifications required to enable proper UART functionality on these pins?

No specific configuration.

I have tested it using a ESP32 S3 Devkit C-1 board using exatly the same sketch reported in this issue ticket and it seems to run fine. No data loss or data corruption. I used a CH340 USB-UART converter attached to pins 19 and 20 and I could send/receive data using Putty and the Arduino Serial Monitor.

Could you please provide some detailed explanation about how to reproduce this issue?
There may be some Python Script to run in the PC side in order to send data and check the integrity in the ESP32-S3 side (and/or vice-versa).

[mightChamp]

Sorry for the delayed response.

We are performing OTA updates via GSM, where the GSM module sends the binary file data over UART (Pins 19 and 20). The update library then writes this data to flash for the firmware upgrade.

Each time, we receive all data bytes; however, the MD5 checksum of the file does not match.

Interestingly, when we switch the UART pins to 17 and 18 and perform the same OTA process, the MD5 checksum always matches.

We have thoroughly checked the hardware and found no issues on that front.

[SuGlider]

I think that it could be a possible level problem.
What about adding some pull-up resistors to the pins 19 and 20?

You can also try adding this to the code:

void setup(){
  Serial.begin(115200);
  // pinMode will force enabling the internal pullup resistor (IDF 5.3.2 Change)
  pinMode(19, INPUT_PULLUP);
  Serial1.begin(115200,SERIAL_8N1,19,20);
}

void loop(){
  while(Serial.available())Serial1.write(Serial.read());
  while(Serial1.available())Serial.write(Serial1.read());
} 

[mightChamp]

Apologies, I forgot to mention earlier that I'm using 4.7K external pull-up resistors on both IO19 and IO20. However, while using pull-ups on GPIO17 and GPIO18 works fine with no UART data corruption, switching to IO19 and IO20 leads to data corruption issues.