I plugged a no-name 80 mm thermal receipt printer into a Printercow dongle and asked ChatGPT to print a test. A few prompts later I had a receipt design, a template with variable line items, and a script that prints it from my own code.
BYSEBASTIAN KLEINBUILDS PRINTERCOW
Receipts are the most common thing a thermal printer does, and the hardest to get right by hand: umlauts and the € sign, a logo, a list of items of any length, totals that line up. I wanted to see whether I could get from a bare printer to a receipt my own code prints, by talking to ChatGPT.
The dongle goes into the printer's USB port and joins the Wi-Fi from the setup page. On the dongle page I set the paper width to 80 mm. That is all a receipt printer needs: Printercow draws every receipt for that width itself, so there is no recipe to write or approve.
I added Printercow as an app in ChatGPT with the MCP URL from the Connect page and signed in once. Then I asked whether it can see my dongles.
siehst du meine dongles?
It listed both of my Rev C dongles: one offline, and the one with the printer online, "printer-80" with 80 mm paper.
I kept it short on purpose.
druck mal einen test
A test receipt with normal and large type, umlauts and the € sign. Then ChatGPT went further on its own and designed a whole receipt: "ORBIT 21", a restaurant on the moon in the year 2091, with a big logo, a menu and a bold total.
The first big graphic on a printer Printercow has not seen before prints only its top strip, and Printercow asks on the dongle page whether it came out clean. I answered yes, and the rest of the receipt printed. Since then every receipt on this printer prints in one go. "Check this printer" on the dongle page does the same up front.
I liked the receipt, so I asked ChatGPT to keep it with everything that changes as a parameter.
Speicher das als Template. Mach alles wichtige wie Quittungsnummer, Positionen, Beträge, QR Code variable bitte
Saved as "orbit-21-restaurant": receipt number, date, table, line items with quantity and prices, taxes, total, payment details and the QR content are parameters. The receipt grows with the number of items.
Then a stress test with a long list.
Simulate as if you would buy a lot of apple products. Print a new Beleg now
18 Apple products for a made-up 9,612.00 €, every line, the tax breakdown and the QR code on one receipt.
Finally I wanted the receipt without any AI in the loop.
Ok provide a script now so that I can print these types very fast via code only as rest endpoint
ChatGPT wrote a small script against the Printercow REST API. Today the template's own page has that code ready to copy, in curl, JavaScript and Python.
A print job waits its turn on the printer, and the Idempotency-Key, here the order number, makes sure a retry never prints twice. "Use from code" on the template's page fills in its parameters.
The API reference lists every call, its fields and its answers.
1 curl -X POST https://milk.printercow.com/api/v1/print-jobs \ 2 -H "Authorization: Bearer $PRINTERCOW_TOKEN" \ 3 -H "Idempotency-Key: order-1042" \ 4 -H "Content-Type: application/json" \ 5 -d '{"dongleId": "dev_...", "template": "orbit-21-restaurant", "params": { ... }}'