UART B/C Iris Carrier Board X16 connector


I am having trouble with the Iris Carrier board with UART communication a RN41 Bluetooth card. I know the level for the card are TTL and not RS232.

I am not able to receive any communication from the Bluetooth card on UART_B (pins 31 and 32 on X16), but strangely I am able to send without a problem.

I have followed the instructions to disable full RS232 on X14 by setting pin 104 to low, but this does not seem to make any difference.

I am using a PXA300 and Windows CE 6.0.

Also Iris Carrier board is v1.1A

Any help would be appreciated.



Hi Nick,
Can you try to measure the signals. First of all to confirm that the voltage levels are OK and secondly to see if the BT device really doesn’t send anything or if it’s more on the reception side of the module.

We did do that, but we have ordered another BT device to see if that was faulty. The loopback test was failing

This problem has been solved and was not a Toradex problem at all but an issue with the default hardware flow on my RN41 Bluetooth adaptor. Shorting out the CTS and RTS pins meant it started to work.

Interesting that setting pin 104 hi or low makes no difference the UART_B still works.

Thanks for the clarification. Note: Even if it works with enabled transceivers, I recommend not using them (set SODIMM pin 104 to low) as otherwise the RS232 transceiver and your BT device drive against each other which might break something or also lead to wrong data reception on the computer module side.