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https://github.com/dan-rodrigues/pico-hx

PCB combining Raspberry Pi Pico and iCE40 FPGA
https://github.com/dan-rodrigues/pico-hx

fpga ice40 kicad pcb raspberry-pi rp2040

Last synced: 3 months ago
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PCB combining Raspberry Pi Pico and iCE40 FPGA

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README 

        
# PicoHX



This is an FPGA board that combines an iCE40 HX FPGA with the Raspberry Pi Pico. The Pico can program the FPGA over USB using a script included in this repo and then interact with it using GPIO.



## KiCad rendering



![PCB rendering](doc/render.png)



## DVI Demo



Pictured is an included DVI demo. First, the RP2040 was programmed with the USB software which then exposes a USB programmer device to the host. Then, the FPGA configuration containing the DVI test pattern config was uploaded from the host to the RP2040, which then programmed the FPGA, which then displayed the test pattern on screen. [This DVI PMOD](https://1bitsquared.com/collections/fpga/products/pmod-digital-video-interface) was used.



![PCB DVI demo](doc/pcb1.jpg)



## Features



* iCE40 HX FPGA (TQFP144, 1k pinout assumed)

* 10 Pico GPIOs connected to FPGA

    * 2 are connected to `GBIN` inputs

* 4x PMODs in a 2x double-PMOD arrangement

* 8x user LEDs for FPGA

* 1x CDONE LED

* 2x users buttons for FPGA

* 1x user button for Pico

* `RUN` button for Pico

* Headers for Pico SWD and hardware UART

* Footprint for QSPI PSRAM or flash

* Micro SD card slot



## Design



### Programming



All iCE40 configuration pins are routed to the RP2040 GPIO so the details of how or when it is programmed are up to the software. The included software in this repo will make the Pico present itself is a USB device with these interfaces:



* Vendor programmer interface: This is how the user can program the iCE40 at any time over USB, using the included [picoprog.py](scripts/picoprog.py) script.

* CDC UART: This UART is separate to the hardware UART that is available on the dedicated pin header. By default, `stdout` is sent to the CDC UART for convenience.



### FPGA clock



The pico exposes one pin that can directly output a clock from one of its PLLs with an optional divider. In the demo software, the USB PLL (48MHz) is divided by 4 to output a 12MHz clock for the FPGA. On the FPGA side, the `GBIN5` pin is used for clock input so that the  `SB_PLL40_2F_PAD` can be used.



### Power



There is only a 1.2v regulator on the board as the Pico provides a 3.3v output. The `2V5_VPP` input is tied to 3.3v as the NVCM isn't used in this project.



### PIO support



The 10 GPIOs connected to the FPGA and 4 GPIOs connected to the SD card slot are in consecutive order, so PIO can be used.



## Demo



A demo that displays several test patterns controlled by BTN-A and blinks the LEDs in succession can be found in [rtl/demo](rtl/demo).



```

cd rtl/demo

make prog

```

 

## Usage



### Building Pico software



It's assumed that the [pico-sdk](https://github.com/raspberrypi/pico-sdk) is installed and the required environment variables are set.



```

cd software

mkdir build

cd build

cmake ..

make

```



The software can then be flashed using `picotool` for example. Default behaviour of the software is to immediately flash the iCE40 with an included bitstream that runs a counter with output to the 8 user LEDs.



### Programming iCE40 bitstream



It's assumed that the OSS FPGA toolchain is installed which includes [yosys](https://github.com/YosysHQ/yosys) and [nextpnr-ice40](https://github.com/YosysHQ/nextpnr).



After the Pico software is flashed, it's ready to program the iCE40 using a custom USB driver script. The script is written in Python3 and requires [pyusb](https://github.com/pyusb/pyusb).



```

pip3 install pyusb

```



It can then be programmed with similar usage to [iceprog](https://github.com/YosysHQ/icestorm/tree/master/iceprog). The programmer script is [picoprog.py](scripts/picoprog.py).



```

./picoprog.py bitstream.bit

```