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Topic: Testing UART with a Buspirate v3 board (Read 695 times) previous topic - next topic

Testing UART with a Buspirate v3 board

I recently acquired a BusPirate v3 and am still quite new to how it works. I have successfully used it to extract firmware from a EEPROM and have managed to update the firmware. It seems that v6.3 of the firmware has a broken Live monitor and Transparent bridge in UART mode (no comms at all) so I had to revert back to 6.2, but that's another story.

I am trying to test serial comms on an Arduino.The first step was to test the UART. For this I have held the Arduino processor in RESET by connecting RESET to GND to prevent it running a sketch and interfering. I have the BP connected to the Arduino with MISO->Rx(UART Tx) and MOSI->Tx(UART Rx). I amd connected with PuTTy to the Arduino and with another PuTTy session to the BP. Baud rates are the same for both sessions. I'm running in open collector mode with pullup resistors enabled.

When I type something on the BP terminal, it comes up in the Arduino terminal, but not the reverse. I have one way comms only. If I disconnect RESET from GND to start the processor and move MISO to Tx and leave MOSI disconnected, I can monitor the processor responses to serial comms using Live Monitor.

So why do I only have one way comms in Transparent bridge?

Re: Testing UART with a Buspirate v3 board

Reply #1
Sorry, I answered in the wrong thread!

Be seeing you.


Re: Testing UART with a Buspirate v3 board

Reply #2
In Arduino reset line is tied to RTS pin of FTDI with a resistor and DTR with a cap. Probably that is messing things up, especially if you set up flow control in the terminal.

Re: Testing UART with a Buspirate v3 board

Reply #3
Thanks for the reply. In the end I came to the same conclusion, namely that the processor, even when held in reset, must be holding something in a state where comms between the UART and device connected to pins 0/1 could not happen properly. I gather that the UNO R3 has only one serial port which is why pin 0/1 are shared with both the UART and CPU. I guess the only way serial comms can work on pin 0 and 1 is if USB is disconnected.


Re: Testing UART with a Buspirate v3 board

Reply #4
Quite possible. As the problem is from Arduino terminal to BusPirate terminal, probably TX pin of the uC is pulled high or low and that is causing problems.

If you can remove the uC from the Arduino board, that will fix things.