Issues running UART TSI on Nexys Video with GemminiNoDDR15MHzNexysVideoConfig - Stuck at "Wrote 0"

[Musa Kartal Engin]

Soru İçeriği (Body):

Hi everyone,

I'm trying to bring up Gemmini on a Nexys Video board using the 

GemminiNoDDR15MHzNexysVideoConfig from Chipyard. I'm facing issues establishing the UART TSI connection.

Problem Description: The bitstream is generated successfully, and I can program the FPGA. Heartbeat LEDs (LED 0 and LED 1) start blinking, indicating the system clock is running. However, when I try to load a test binary using 

uart_tsi, the tool connects but then hangs indefinitely during the loading phase.

Command Used:

bash

sudo ./uart_tsi +tty=/dev/ttyUSB1 +baudrate=115200 +verbose ./test_mvin_mvout.riscv

Logs: It repeatedly prints 

Wrote 0, suggesting it's sending data but not receiving any acknowledgement or response from the FPGA.

UART-TSI: Attempting to open TTY at /dev/ttyUSB1

UART-TSI: Checking connection status with /dev/ttyUSB1

UART-TSI: Connection succeeded

UART-TSI: Loading program

UART-TSI: Wrote 0

UART-TSI: Wrote 0

... (hangs here forever)

Observations:

• LED 0 & 1: Blinking correctly (system heartbeat seems alive).
• LED 3 (dropped): No activity.
• LED 4-7 (TSI state): No activity observed during the loading attempt. It seems the UART hardware on the FPGA is not processing or detecting the incoming packets at all.

Environment:

• Board: Digilent Nexys Video (Artix-7)
• Chipyard Config: GemminiNoDDR15MHzNexysVideoConfig
• Host: WSL2 (Ubuntu) with USB-UART forwarded properly.

Has anyone successfully used this specific 15MHz NoDDR configuration? Are there any specific baud rate settings, clock constraints, or extra arguments required for 

uart_tsi to work with this low-frequency config?

Thanks in advance!