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Introduction

This is a special distribution of the Raspberry Pi OS for Raspberry Pi 3, 4 or 400, which contains a complete development environment for the Orange Cartridge. Two example applications are also included.

The script build.sh creates the distribution using a Docker. This has been tested on 64-bit ARM only, other platforms may work but are not supported. Don't forget to fetch the git submodule first.

Alternatively, download a prebuilt image from the download area.

Installation

To install, write nnnn-nn-nn-Raspbian-64bit-ocdevenv.img to an SDcard of at least 16 MiB in size. Insert the card in Raspberry Pi 3, 4 or 400, and power it up. After completing the regular Raspbian setup process, please reboot the system at least once in order for the larger swap setting to kick in (important if the Pi has less than 4G of RAM).

Building the sample applications

super-reu

To build the super-reu, cd into the directory super-reu, and run make. The build should complete within a few minutes. To flash the built image, run make flash. (Make sure the Orange Cartridge is connected to USB, and is in bootloader mode.)

RVCop64

To build the RISC-V coprocessor application, cd into RVCop64/hw and run ./bitstream.py --platform orangecart. On a Raspberry Pi 3 this can take up to 15 minutes due to the constrained RAM in that model. To flash the build image, run dfu-util -a 0 -D build/gateware/orangecart.bit -R. (Make sure the Orange Cartridge is connected to USB, and is in bootloader mode.)

40-pin GPIO connector

The 40-pin GPIO connector on the Raspberry Pi can be used for some extra functionality:

• JTAG
• Debug UART (if the bitstream programmed into the FPGA implements one)
• Red/green LED (with cartridge breakout board only)

These are all optional functions, the USB cable is sufficient for basic use.

The following table shows the appropriate connections to the "SWD" style connector on the cartridge itself, to a 20-pin JTAG adapter such as https://www.adafruit.com/product/2094, or to the 20-pin "3B" connector on the cartridge breakout board.

3.3V need only to be connected to the breakout board for LED operation. Do not connect the Pi:s 3.3V to 3.3V/VCC/VREF in the JTAG connector.

Always connect GND, even if just using the serial port and/or LEDs.

JTAG

OpenOCD has been set up to automatically connect to the ECP5 using the JTAG interface on the 40-pin header.

UART

On a Raspberry Pi 4 or 400, /dev/ttyAMA1 is connected to UART5 on pin 32 and 33. Note that RXD on the cartridge needs to be connected to TX on the UART, and vice versa (zero modem).

Pi 3 does not have UART5 on pin 32/33. Connect RXD/TXD elsewhere if needed.

LEDs

To control the LEDs on the breakout board, first enable the GPIO using

echo 19 > /sys/class/gpio/export

Then use the following commands:

echo low > /sys/class/gpio/gpio19/direction # Red
echo high > /sys/class/gpio/gpio19/direction # Green
echo in > /sys/class/gpio/gpio19/direction # Off