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build License: GPL v3

PICO Firmware

This folder contains the firmware for the PICO.

Compilation

mkdir build-firmware
cd build-firmware
cmake ../firmware
make -j9

Next, copy the sst39sf040.uf2 file from the build folder to your PICO.

Toolchain

First install the following packages

sudo apt update
sudo apt install -y cmake gcc-arm-none-eabi libnewlib-arm-none-eabi \
build-essential libstdc++-arm-none-eabi-newlib

Next, install the toolchain

sudo git clone https://github.com/raspberrypi/pico-sdk.git /opt/pico-sdk
sudo git -C /opt/pico-sdk submodule update --init
echo 'export PICO_SDK_PATH=/opt/pico-sdk' | sudo tee -a /etc/profile.d/pico-sdk.sh
source /etc/profile

UART commands

The PICO exposes a COM port for interdevice communication. All commands have a fixed width of 8 characters, which is echoed back. Depending on the command, either the PICO expects to receive another chunk of data or returns more output. The list of commands are given below.

  • READINFO: Reads the board ID. Returns 16 bytes of data.
  • RDBKXXXX: Reads a block of data (256 bytes) at hex position XXXX00. Returns 256 bytes of data.
  • RDSECTXX: Reads a sector of data (4kb) at hex position XX000. Returns 4kb bytes of data.
  • RDBANKXX: Reads a bank of data (16kb) where XX corresponds to the bank id.
  • RP2KCRXX: Reads a block of data (0x1000 bytes) at hex position XX000. Returns 0x1000 bytes of data. This function is used to interface with the P2000T cartridge, do not use this function when reading from a regular ROM chip.
  • DEVIDSST: Attempts to read the device ID of the SST39SF0x0 chip. Returns 2 bytes of data.
  • WRBKXXXX: Write a block of data at hex position XXXX00. Expects 256 bytes of data after the command echo. Returns 1 byte checksum.
  • WRSECTXX: Writes a sector of data (4kb) at hex position XX000. Returns a CRC16 XMODEM checksum (2 bytes).
  • ESSTXXXX: Erases a block of data (writing 0xFF) at hex position XXXX000. Returns number of wait cycles as 16 bit signed integer.
  • ERASEALL: Completely wipes the chip, writing 0xFF to all bytes.
  • TESTTEST: Simple test routine. Reads the first 32 bytes on the chip. Returns 32 bytes of data.