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qmtech_ep4ce15.py serial port definition "rx", Pins("J3:8") or Pins("J3:9") in linux-on-litex-vexriscv application #232

Closed marconi1964 closed 2 years ago

marconi1964 commented 3 years ago

Hi,

I got a chance to know LiteX recently from my friend who gave me a QMTech_EP4CE15F23C8N board, and practice linux-on-litex-vexriscv on it.

My friend told me to connect my USB-UART serial port to J3:7 and J3:9 (J3 is U8 on the qmtech board), which works well. But when I check this settings litex-boards/litex_boards/platforms/qmtech_ep4ce15.py regarding Serial port definition below, I am confused. The setting is J3:7 and J3:8 (instead of 9). So I am wondering if the Serial port used in linux-on-litex-vexriscv is defined elsewhere, and not here?

# file name : litex-hub/litex-boards/litex_boards/platforms/qmtech_ep4ce15.py 
# ......

    # Serial
    ("serial", 0,
        # Compatible with cheap FT232 based cables (ex: Gaoominy 6Pin Ftdi Ft232Rl Ft232)
        Subsignal("tx", Pins("J3:7"), IOStandard("3.3-V LVTTL")), # GPIO_07 (JP1 Pin 10)
        Subsignal("rx", Pins("J3:8"), IOStandard("3.3-V LVTTL"))  # GPIO_05 (JP1 Pin 8)
    ),

# ......

    ("J3", {
        # odd row     even row
         7: "AA13",   8: "AB13",
         9: "AA14",  10: "AB14",

Thank you,

enjoy-digital commented 2 years ago

Hi @marconi1964,

the pinout used by Linux-on-LiteX-Vexrsicv for the serial is the one defined in LiteX-Boards, so if there is an issue/inconsistency, it's in qmtech_daughterboard.py/``qmtech_ep4cex5.py platform files.

@hansfbaier: Do you have an idea on this? Are you using J3:8 as FPGA TX and J3:7 as FPGA RX?

hansfbaier commented 2 years ago

@marconi1964 The board platform files for EP4CEx5 specify:

            Subsignal("tx", Pins("J3:7"), IOStandard("3.3-V LVTTL")),
            Subsignal("rx", Pins("J3:8"), IOStandard("3.3-V LVTTL"))

Which means you should wire your UART tx to J3:8 and UART tx to J3:7 (if I'm not mistaken). The linux on Vexriscv project uses the serial from the platform file, so it should work with the pins specified in the platform file. Maybe your friend uses another board?

enjoy-digital commented 2 years ago

We can probably close this now.