# How to see the px4iofirmware/mixer.cpp debug message?

**URL:** <https://discuss.px4.io/t/how-to-see-the-px4iofirmware-mixer-cpp-debug-message/11640>\
**Category:** Pixhawk\
**Created:** [June 27, 2019, 6:31am UTC](https://discuss.px4.io/t/how-to-see-the-px4iofirmware-mixer-cpp-debug-message/11640 "2019-06-27T06:31:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Evaneee](https://discuss.px4.io/letter_avatar_proxy/v4/letter/e/85f322/32.png) [@Evaneee](https://discuss.px4.io/u/Evaneee)\
**Post date:** [June 27, 2019, 6:31am UTC](https://discuss.px4.io/t/how-to-see-the-px4iofirmware-mixer-cpp-debug-message/11640/1 "2019-06-27T06:31:28Z")

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Connect to pixhawk4 with FTDI cable,  
I want to debug mixer.cpp, and want to see debug message in the code  
`isr_debug(1, "AP RX timeout");`  
–try `px4io debug 5`，nothing happened  
–write some “printf”to mixer.cpp, cant see any message from nsh  
–move FTDI cable to IO debug port, there will be black squares, or some gibberish

* * *

when the cable connect to fmu debug port, it works well

 ![image](https://discuss.px4.io/uploads/default/original/2X/2/24b5b80285903c5a76992395a6a1f3cda43edf39.png)  
The same cable connect to IO debug port, it will be  
 ![image](https://discuss.px4.io/uploads/default/original/2X/d/d68154f01cd3c14b51a1560168184392b74d8455.jpeg)

does anyone knows how to see IO debug message or what’s wrong with my cable?? Many thanks

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<div class="post-metadata">

**Author:** ![dlwalter](https://discuss.px4.io/user_avatar/discuss.px4.io/dlwalter/32/3011_2.png) [@dlwalter](https://discuss.px4.io/u/dlwalter)\
**Post date:** [June 27, 2019, 2:02pm UTC](https://discuss.px4.io/t/how-to-see-the-px4iofirmware-mixer-cpp-debug-message/11640/2 "2019-06-27T14:02:22Z")

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Try changing the baudrate to 115200.

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<div class="post-metadata">

**Author:** ![Evaneee](https://discuss.px4.io/letter_avatar_proxy/v4/letter/e/85f322/32.png) [@Evaneee](https://discuss.px4.io/u/Evaneee)\
**Post date:** [June 28, 2019, 12:24am UTC](https://discuss.px4.io/t/how-to-see-the-px4iofirmware-mixer-cpp-debug-message/11640/3 "2019-06-28T00:24:45Z")

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It works  
Thanks  
vvvvvvvvvvvvvvvvvvvvvvvvvvvvery  
much!!!