photopainter-jpg

Firmware for the Waveshare PhotoPainter that reads JPEGs straight off the SD card.

The stock firmware only shows 24-bit BMPs in the exact panel palette, so every photo has to go through Waveshare's converter tool first. For me it was not handy at all, so I've decided to get rid of the converter tool & enable support for JPG natively.

So now you have to: put .jpg files in pic/, done. No WiFi, no app, no cloud.

Flash it

1. Grab photopainter-jpg.uf2 from Releases.
2. Hold BOOT, plug in USB, release. A drive called RPI-RP2 shows up.
3. Copy the .uf2 onto it. The frame reboots on its own. Done.

Use it

Put your photos in a folder called pic on the SD card:

pic/
  IMG_0234.jpg
  mum.jpg
  cat.bmp

Any size, any aspect ratio, straight from a phone. The frame picks the next one every 24 hours, sorted by filename. BMPs still work like before. You can manually enforce a change by clicking the "NEXT" button on your photopainter.

What it does to your photos

• Scales down & center-crops to 800×480, so the picture fills the panel
• Portrait photos get turned 90°, so they fill the panel too, you can turn the frame on its side. If they end up rotated the wrong way for you, flip PORTRAIT_CW in lib/GUI/GUI_JPGfile.c.
• Reads EXIF orientation, so phone pictures aren't sideways
• Floyd-Steinberg dithering against the colours the panel actually produces, not the ideal RGB values. Skin tones & skies come out noticeably better than with a naive palette match.

A 12 MP photo takes about 15 seconds to decode, plus the ~33 seconds the panel needs to refresh. The RP2040 runs at 250 MHz for this.

Seven colours & a dusk sky is about the hardest thing you can ask of this panel but it holds up!

Change the interval

In main.c:

alarmTime.hours += 24;      // every 24 hours
// alarmTime.minutes += 30; // every 30 minutes

Then rebuild.

Build it yourself

You need the Raspberry Pi Pico extension for VS Code — it installs the SDK & the ARM toolchain for you. Open the folder, run Raspberry Pi Pico: Import Project, then Compile. The .uf2 lands in build/.

From a terminal it's the usual:

cmake -S . -B build -G Ninja
ninja -C build

Which hardware

Waveshare sells several frames called PhotoPainter. This one is for the original PhotoPainter: RP2040, 7.3" 7-colour ACeP panel.

Model
PhotoPainter (RP2040)	this one
PhotoPainter (B) — Pico 2, Spectra 6	small port, see below
ESP32-S3-PhotoPainter	no & it doesn't need one — that firmware already decodes JPEG
RPi Zero PhotoPainter	no, that one runs Linux, where Pillow does the job in ten lines

Porting to the (B) is not much work: the pinout is the same, so it comes down to swapping lib/e-Paper for its EPD_7in3e driver, setting PICO_BOARD pico2 & rewriting PAL[] in lib/GUI/GUI_JPGfile.c for the six Spectra colours -> no orange & the indices are different. Open an issue if you have one & want to try it, I don't have the hardware here.

Limits

• Baseline JPEG only. Progressive JPEGs get a message on the panel instead of garbage. Phone and camera photos are baseline; some web downloads aren't.
• No HEIC. Export as JPEG.
• 8.3 filenames are safest. Long names work but FatFs is picky about some characters.

Credits

Built on Waveshare's PhotoPainter firmware and ChaN's TJpgDec. Panel colour values borrowed from Pimoroni's Inky library, which has clearly spent more time staring at these things than I have.

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Built by Alexander West.