💸 CYD PromptPay Terminal (Stripe)

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A tiny self-contained payment terminal: an ESP32 with a 2.8" touch screen that displays a Thai PromptPay QR generated through Stripe, then flips to a green success screen (with a beep!) the moment the customer's payment lands.

boot ─▶ WiFi ─▶ enter amount on touch keypad ─▶ create QR via Stripe ─▶ show QR
                     ▲                                                  │ poll every 3 s
                     │              tap screen                          ▼
                     ◀────────────────────────────────────  PAYMENT RECEIVED ✓

1. Enter the amount on the on-screen keypad (minimum 10 THB — Stripe's floor for PromptPay)
2. The board creates a PaymentIntent (amount, currency=thb, payment_method_types[]=promptpay, confirm=true) — one call to the fully documented Stripe API, and the response already contains the EMVCo QR payload
3. The QR renders on the white card; the board polls the PaymentIntent every 3 seconds
4. succeeded → full-screen green check + beep. Tap to return to the keypad.

No Payment Link needed — a single secret key is enough to take payments.

The library also keeps a legacy createQr() that derives the QR from a Payment Link via Stripe's undocumented checkout endpoints. It breaks with payment_method_types_mismatch when the link doesn't offer PromptPay — prefer createQrDirect().

All three values come from the Stripe Dashboard:

PromptPay must be enabled in Settings → Payment methods (Thai Stripe accounts).

• Keys live in include/secrets.h, which is gitignored. Copy the template and fill it in:

  cp include/secrets.h.example include/secrets.h

• The secret key can move money-related state on your account. If it ever leaks — a screenshot, a pastebin, a committed file — roll it immediately: Dashboard → Developers → API keys → ⋯ → Roll key.

• Better: instead of sk_live_..., create a restricted key (Developers → API keys → Create restricted key) with only PaymentIntents read/write — that's all this project needs.

• TLS note: the firmware uses setInsecure() (no certificate pinning), standard practice on ESP32 hobby projects but worth knowing.

Runs on a 2.8" ESP32 display board of the CYD family (pinout-compatible with the well-documented ESP32-2432S028R). Everything is on the board — screen, touch, speaker for the payment beep. No wiring.

👉 The exact board used: Shopee listing

If colors look inverted remove -D TFT_INVERSION_ON=1 from platformio.ini; if touch is offset adjust touch.setCal(...) in src/main.cpp.

git clone https://github.com/moomdate/CYD-PromptPay-Terminal.git
cd CYD-PromptPay-Terminal
cp include/secrets.h.example include/secrets.h   # fill in WiFi + Stripe values
pio run -t upload

The screen walks through: connecting WiFi → amount keypad → QR screen with the amount → success screen. Errors show Stripe's message with a tap-to-retry.

Configuration in include/secrets.h:

The Stripe logic is a standalone library published on the PlatformIO Registry (source) — use it in any project:

lib_deps = moomdate/StripePromptPay @ ^1.0.0

#include <StripePromptPay.h>

StripePromptPay stripe;
stripe.begin(STRIPE_PK, STRIPE_SK);

if (stripe.createQrDirect(1000, "you@example.com")) {  // 10.00 THB
  render(stripe.qrData());                 // EMVCo payload for any QR lib
  String st = stripe.paymentStatus();      // "requires_action" → "succeeded"
}
Serial.println(stripe.lastError());        // populated on failure

It has no display dependencies — just WiFi + ArduinoJson — so it works on any ESP32.

include/
├── secrets.h.example  # template — copy to secrets.h (gitignored)
src/
├── main.cpp           # UI: amount keypad, QR card, polling, success screens
├── lang.h             # EN/TH string tables (UI_LANGUAGE)
├── fonts/             # Sarabun (OFL) smooth fonts with Thai glyphs
tools/gen_vlw.py       # regenerate the fonts from any OFL TTF

Stripe logic comes from the StripePromptPay registry package.

MIT