P1 bringup: PS UART1 Tx/Rx line inverted on FTDI chip
UART1 lines on PS:
- PS_USB_UART_RX: PS MIO73 (Rx, Input)
- PS_USB_UART_TX: PS MIO72 (Tx, Output)
As indicated on the following Xilinx support thread: "PS UART Rx and Tx MIO pins are hardwired and cannot be swapped"
UART1 lines on FTDI2232HL (IC11):
- PS_USB_UART_RX: pin 39: BDBUS1 (RXD)
- PS_USB_UART_TX: pin 38: BDBUS0 (TXD)
As we can see, PS Rx (input) is connected to FTDI Rx (input), and PS Tx (output) is connected to FTDI Tx (output)
Fix
A simple and temporary fix is to swap Rx and Tx lines just before IC11, by removing R361 and R362 and soldering wires from PS Tx to FTDI Rx and from FTDI Tx to PS Rx