Why does my ESP32 crash only if I use Serial?

Using Arduino Programming Questions
1

I wrote some code to intercept a UART connection. So my wiring is:

DEVICE1_TX -> [GPIO11 - ESP32-S3 - GPIO12] -> DEVICE2_RX
DEVICE1_RX <-  [GPIO13 - ESP32-S3 - GPIO14] <- DEVICE2_TX

GPIO11 and GPIO12 mapped to UART1 (@115200)
GPIO14 and GPIO13 mapped to UART2 (@115200)
UART0 is just used for debug messages (@921600, but tried lower baud rates too)

As long as I don't print anything on UART0, everything seems to work just fine and if I only print very short/few messages on UART0, everything keeps working fine for a minute or so.
But as soon as I print for example all messages received from UART1 and UART2 on UART0, it keeps crashing almost immediately with a weird looking message that I don't understand:

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x42024902
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbec
load:0x403cc700,len:0x2920
entry 0x403c98d8

In reality it looks more like this:

Debug Serial initialized

UART Interceptor ready

test...
test...
test...
test...
tesESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x42024902
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbec
load:0x403cc700,len:0x2920
entry 0x403c98d8
Debug Serial initialized

UART Interceptor ready

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x42024902
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbec
load:0x403cc700,len:0x2920
entry 0x403c98d8
Debug Serial initialized

UART Interceptor ready

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x42024902
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbec
load:0x403cc700,len:0x2920
entry 0x403c98d8
Debug Serial initialized

UART Interceptor ready

test...
test...
test...
test...
test...
tESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x42024902
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbec
load:0x403cc700,len:0x2920
entry 0x403c98d8

Unfortunately I can't really provide a test sketch because of the complexity of needing to have 3 separate devices, but I'm basically just using this class UARTInterceptor.cpp along with some Serial.prints.

Am I missing anything obvious?

At first I thought SoftwareSerial might be the issue, but since the ESP32 can map the 3 hardware serial UARTs to any pin, I switched to HardwareSerial, but I'm still having these issues.

I also tried increasing the baud rate of UART0 to way more than UART1+UART2 together, but it's still not working reliably.

Is this a common issue? Do I have to increase the ring buffer size or something like that?

I tested this on a standard ESP32 as well as on an ESP32-S3 btw. Same result.

Edit:
One more important detail: If No data is received/sent on UART1 and UART2, I can spam UART0 without any crashes.

Edit2:
The messages I'm dealing with are usually around 15 bytes in size with same exceptions of 234 bytes.

Edit3:
Increased the ringbuffer size to 2048 for tx and rx of UART1 and UART2. Still the same crashes.

2

If I remember well, on standard esp32 gpio 11 is connected to spi flash.

3

But the documentation says:

Pin Headers All available GPIO pins (except for the SPI bus for flash) are broken out to the pin headers on the board for easy interfacing and programming. For details, please see Header Block.

So no matter which pins I use, it should be impossible to accidentally pick the SPI flash ones.

Also the datasheet mentions that any GPIO pins can be assigned for U1TXD_out, U1RXD_in, U2TXD_out and U2RXD_in:

image
image1143×611 18.8 KB

This is the pinout diagram for my board btw:

image
image1584×1080 178 KB

4

You wrote you were trying both, standard and s3. "Standard" has flash pins exposed, 11 being one of them.

5

Yes, I used different pins on the ESP32 board. But got the same crashing behavior.

6

Then really nothing obvious comes to my mind..

7

Okay, I threw away my UARTInterceptor code and started again from scratch. Now it's working. Maybe there was a buffer overflow writing over something important with my old code.