Daft's Emulator for RP2040

This is mostly an extremely hacky PicoSystem emulator.

./DERP_SDL file.uf2

(To run some uf2s built with the PicoSystem SDK add --board pimoroni_picosystem before the file to override the board value)

Bootrom

A copy of the RP2040 bootrom is required in bootrom.bin.

This can be created from the elf files in the official releases:

arm-none-eabi-objcopy -O binary b2.elf bootrom.bin

... or dumped from a real RP2040 with picotool:

picotool save -r 0 4000 bootrom.bin

Feature	Status	Details
Display	Hack	No PIO/SPI, hack in DMA code. (Assumes 32blit-sdk setup)
Buttons	Works
Sound	Works
LED	TODO

Feature	Status	Details
Cortex-M0+	Partial	Copied from GBA emu, so some details are still an ARM7
DMA	Minimal	Implemented just enough for PicoSystem display updates
Clocks	Partial
XOSC	Minimal	Fixed 12MHz
ROSC	Minimal	Fixed 6MHz
PLL	Partial
GPIO	Partial	Missing overrides, partial interrupt handling
PIO	Minimal	PIO0 always returns all FIFOs empty + TXSTALL
USB	Partial	Optional device enumeration and USBIP server
UART	Minimal	Prints TX data
I2C	None
SPI	Minimal	SPI0 TNF always set
PWM	Partial	Enough for PicoSystem beeps
Timer	Partial
Watchdog	Partial	Tick generation and reset timer
RTC	Minimal	Enough to get through init
ADC	None
SSI	Minimal	Just enough to boot

Optional USB support can be enabled with:

./DERP_SDL --usb [...]

This will attempt to enumerate the device and print the output from a CDC interface if found.

Alternatively:

./DERP_SDL --usbip [...]

Will enable a USBIP server. Which can be connected to using something like: (May require some extra sudo)

modprobe vhci-hcd

# check for devices
usbip list -r localhost

# attach device
usbip attach -r localhost -b 1-1

Launching without a .uf2 file does allow using the bootrom's loader. Though this is probably not a good idea...

(Low level transfers/timings are not implemented so the transfer rate for USB data is... unpredictable)