Serial debug on Viola carrier board


Can I safely connect a FTDI adapter to Viola plus carrier board as stated in this page?


I have a TTL-232R 6 pin cable TTL-232R-3V3 Connector and I want to connect

  • GND : viola X9.24 - FTDI #1
  • TX : viola X9.26 - FTDI #4
  • RX : viola X9.27 - FTDI #5

See attached datasheet link text

Thank you

The serial communication works but there is a problem:
Connecting the FTDI adapter, the iMX6 board and the carrier gets extremely hot, and at the end it broke.

Now I have a Colibri broken and unusable.

Hello @koan,
thanks a lot for using the Toradex Developer Community.
I checked the connections that you indicate above and there is something which is not correct in my opinion.
According to the TTL-232R-3V3 datasheet, pin 4 it is the TXD signal which should be connected to the UART_A_RXD signal of the Viola carrier board.
This signal is available on pin 27 of the Extension Header X9. The correct connections should therefore be:

  • FTDI pin 1->Viola X9 pin 24 (GND)
  • FTDI pin 4->Viola X9 pin 27 (TX)
  • FTDI pin 5->Viola X9 pin 26 (RX)

I am not sure what’s the reason for having a working communication.
Do you have another module and carrier to test the connection I recommended?

I hope this helps, please don’t hesitate to get back to me if you need any further help.

Hello @koan,

I would say that if you use the 3.3V level device, it should be working. I think that this was already done in the past but I will have anyway somebody trying this configuration one more time here, and I will get back to you.

Hello @diego.tx

of course the GND,TX,RX were a typo.

In my opinion the issue here was some kind of electrical level when I connect the FTDI.
With the first try I burnt the Colibri.

Afterwards I used another new Viola Plus and another Colibri but I noticed that the board went extremely hot after 5 min. so I disconnected the FTDI.
My situation now is the following:
I prepare the Colibri with a static IP address using an Iris board (the most reliable IMHO), afterwards I mount it on the Viola Plus and I access the console via SSH.

This is a temporary solution, because I’d like to have a serial debug port on Viola Plus.
I do need your confirmation that this is s.afe and doable and won’t burn another Colibri.
Please try on your side and let me know the result.

Thank you

Hi @diego.tx
thank you.

I am using the 3.3V level device I usually use with Raspberry and BeagleBoneBlack.
I am looking forward to receiving the result of your test.

hi @koan

I did the test on Viola Board with a similar TTL USB/Serial Converter with FTDI chip with iMX6DL 1.1A mounted and it is working fine for me.

So let us figure out the issue together.

  1. Are you sure to use 5V Power Supply for Viola Board?
  2. Could you share the picture of your connection?
  3. Could you measure the voltage level at the TX, RX and GND?
  4. Have you done any changes to the Software or are you using the regular Bsp?

Thanks and best regards,

Hi @jaski.tx

  1. Power supply is 5Vcc
  2. please find attached photos
  3. the voltage level at the TX, RX and GND is 4.2Vcc - 3.6Vcc
  4. I didn’t modify anything and I am using the regular BSP

However I found there is a 92Vac tension between the Viola GND and the PC GND.


I changed power supply taking one from another Vendor eval board.
Now the delta between the Viola GND and my PC GND is 13.6Vac only

Hello @koan,

I would not be worried about this voltage between the GND, it has probably to do with the way the power supply is designed.

To me is a bit more frightening the fact that you measuring 4.2V on the TX and RX signals.

Table 4.3.2 TTL-232R-3V3 Electrical Parameters on page 11 of the TTL-232R datasheet, states that the maximum VOH should be 3.2V.

Could you please check one more time this device is actually a 3.3V version one? Maybe it is wrongly labeled and you never noticed because RBPi and BeagleBoneBlack have a 5V tolerant serial interface? Is it possible?

Do you have in your office one additional similar FTDI device, just to make sure it is not damaged and the output voltage is actually too high?

Thanks again for your valuable help in this case.

Another FTDI cable 3V3
Between #24 - #26 : 4.0Vcc
Between #24 - #27 : 3.3Vcc

Another FDI cable, andother Viola board
Between #24 - #26 : 3.3Vcc
Between #24 - #27 : 3.3Vcc

Conclusion: also the Viola board has been burnt.

Problem solved

My Chinese 5V power suppy was defective and caused all the problems and burnt the Viola carrier and the Colibri iMX6.

Further tests demonstrated that it is safe to connect a FTDI adapter to Viola plus carrier board as stated in this page

Thank you everybody!

Perfect that the issue is solved. Thanks for your feedback.