I have an existing design using a TM4C123 part where the RS232 signals are sent to the chip uninverted. My new design is a TM4C129 part and it seems that it wants the signals inverted, though I cannot find any documentation to that effect. Is that true?
Thanks, Doug
Hi Doug,
My new design is a TM4C129 part and it seems that it wants the signals inverted,
TM4C129 should not invert the UARTTX signal. I'm not sure what you mean the signal is inverted. When idle, the TX line should pull up. It asserts TX low when a transaction starts with a START bit. It is per UART protocol. If you are saying during idle the TX is low and the START bit becomes high then it is not possible by design. Can you disconnect UARTTX signal from your device. Do you observe UARTTX with correct behavior? If that is the case, then something is pulling or inverting on the bus at the board level.
TM4C129 UART must obey the protocol as follows.
