/tinyfpga-litex

A minimal LiteX SoC definition for the TinyFPGA BX

Primary LanguagePython

TinyFPGA LiteX

A minimal LiteX SoC definition for the TinyFPGA. Currently, only TinyFPGA BX is supported, but more boards may be added in the future.

Quick Start

  1. Install LiteX according to the Advanced or Medium quickstart guide on LiteX GitHub. Note that depending on what CPU you would like to use (see Caveats below) your target compiler may be available in your system's package manager!

  2. Install LiteX-Boards (depending on your workflow)

     pip3 install git+https://github.com/litex-hub/litex-boards

 - or -

 git clone https://github.com/litex-hub/litex-boards
 cd litex-boards
 python3 setup.py develop
 cd ..

  3. Install tinyprog, if you don't already have it

     pip3 install tinyprog

  4. Clone this repository

     git clone https://github.com/kekiefer/tinyfpga-litex
 cd tinyfpga-litex

  5. Build the SoC:

     python3 tinyfpga_litex.py --cpu-type vexriscv --cpu-variant=lite

  6. Program the gateware bitstream and the firmware:

     tinyprog -p soc_tinylitex_tinyfpga_bx/gateware/top.bin -u soc_tinylitex_tinyfpga_bx/software/userdata.bin

If everything works, you should see output on the UART and a flashing LED.

Footprint --cpu-type vexriscv --cpu-variant=lite

Info: Device utilisation:
Info: 	         ICESTORM_LC:  4565/ 7680    59%
Info: 	        ICESTORM_RAM:    32/   32   100%
Info: 	               SB_IO:    10/  256     3%
Info: 	               SB_GB:     8/    8   100%
Info: 	        ICESTORM_PLL:     0/    2     0%
Info: 	         SB_WARMBOOT:     0/    1     0%

UART configuration

Make sure to connect an UART adapter to the TinyFPGA BX. Floating serial signals result in undefined behavior which can prevent the SoC to boot. I have an FTDI serial cable that plugs directly into pins soldered to the TinyFPGA BX, so I have configured tinyfpga_bx platform definition to add the serial peripheral with the following pins:

(
    "serial", 0,
    Subsignal("tx", Pins("C2")),
    Subsignal("rx", Pins("B1")),
    IOStandard("LVCMOS33")
)

This could be easily reconfigured in any way that suits your application

Caveats

I have tried (not very hard) and failed to run the picorv32 CPU and also failed to run vexriscv variants other than lite. It is probably possible to get these to work, as well as lm32 or other CPUs, as long as the footprint isn't too large.