Hi everyone,
I’ve got corrupted debug output over the serial connection which I’ve not managed to resolve. This is the exact same problem as described in this post: Serial console showing gibberish with Ixora V1.2 and Apalix IMX8 - Technical Support - Toradex Community. I’m using an Apalis iMX8 with v1.3A of the Ixora carrier board.
The corruption is mostly repeatable - for example if I type “a” then “X” is echoed back, or if I type “s” then “.” is echoed.
I have checked and re-checked the following:
baud rate, parity, stop-bits and flow control
pinout on the connector
tried two types of serial convertor (TTL-232R-RPi or DTECH 3 Pin USB to TTL Serial 3.3V)
two different laptops
different ports on the laptops (including those with USB 2 instead of 3)
different images (both the Acontis Ethercat image and the standard Toradex Linux image)
When I boot the board I receive characters, but they are also corrupted.
I’ve run out of things to try, so any help would be appreciated!
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Hello, and thank you for reaching out!
Based on your setup (Apalis iMX8 with Ixora v1.3A), here are the key points to check for reliable serial console output:
Correct UART Adapter:
The Apalis iMX8 console is on X22 of the Ixora board, which is a 10-pin IDC header. Toradex recommends using their DB9 to IDC adapter cable, which uses the DTK/Intel standard pinout. If you’re using a different cable, verify the pin mapping matches the official standard.
Null-Modem/Crossover Required:
Ensure you use a nullmodem-crossover connector between the cable and the USB serial adapter. Without the crossover, transmit/receive lines may not align, resulting in “gibberish” output or incorrect echoes on keypresses. See serial connection requirements
USB-to-TTL Adapter Caveats:
If using USB-to-TTL converters (such as TTL-232R-RPi or DTECH), ensure:
The voltage levels match (3.3V logic recommended)
The TX/RX mapping corresponds to the Apalis UARTpinout
Ground is connected between your adapter and the Ixora board
Cable Connection:
Double-check the cable is fully and securely seated on X22.
Test Straight DB9-to-DB9:
If available, attempt using a straight DB9 serial cable with a null modem adapter instead of USB-to-TTL options.
General Troubleshooting Steps:
Try swapping TX and RX lines on your USB-to-TTL adapter in case of confusion.
Confirm other devices (if available) can correctly receive serial output from your adapter to rule out hardware problems.
Test with a different terminal emulator on your laptop (for example, try minicom, PuTTY, or Tera Term).
The repeating “key X = echoed Y” behavior is classic for a receive-data (RX) and transmit-data (TX) swap or incorrect/null modem cable usage.
@ToradexAI - I can confirm that swapping the TX/RX cables doesn’t help. Although, surprisingly, I do still receive characters during boot up. I’ve also tried plugging the RX cable into every other pin on the connector (with the TX cable disconnected).
I’ve also reproduced the problem with different terminal emulators.
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Thank you for the additional details.
Given your tests with swapping TX/RX, different adapters, and terminal emulators, it’s important to emphasize that the X22 connector on the Ixora board is an RS232-level debug header, not a direct 3.3V/TTL UART. Most USB-to-TTL cables (including TTL-232R-RPi and the DTECH 3 Pin USB to TTL Serial 3.3V) work at 3.3V logic level, but the Apalis X22 header provides standard RS232 voltage levels.
Connecting a TTL-level adapter directly to the RS232 lines can cause data corruption because TTL and RS232 use different voltage levels and signaling conventions. This often results in the “gibberish” or shifted character behavior you describe.
To reliably use the serial debug console on Ixora:
Use a proper RS232-to-USB adapter (with DB9 connector).
Use the correct 10-pin IDC to DB9 (male) adapter with DTK/Intel standard pinout.
Insert a null modem (cross-over) cable between the DB9 cable and your RS232-to-USB adapter to ensure proper TX/RX crossover.
Confirm the serial terminal parameters as follows:
115200 baud, 8 data bits, no parity, 1 stop bit, no flow control.
More information and a wiring diagram can be found here:
Board reference:
In summary, the key problem is likely a mismatch between TTL and RS232 voltage levels. Using an RS232-level serial adapter (not TTL-level) is required for the debug port on Ixora with Apalis modules.
Let me know if you have any questions or need clarification regarding the recommended connection.
Unfortunately, you didn’t specify which UART you were trying to use or how exactly you connected the listed serial cables to the Ixora board.
If you are referring to UART1 (Console/Debug) and connected the cables to the X22 connector on Ixora, it definitely will not work. UART1 on the Ixora board is only accessible through a TTL-to-RS232 level shifter, and its signal levels are not compatible with the cables (adapters) you mentioned. You’ll need to use a cable like this one, or any other model that supports RS232 signal levels
Thanks for the quick reply. Yes, I am using X22 and it sounds like the RS232 vs TTL levels are the problem. I’ll try with a more appropriate usb to RS232 cable today and post back with the results.
