What you need
An iPad or iPhone running the Common Ground POS app Version 1.10
A Star mPOP (mC-P21 / mC-P31)
The mPOP powered on and connected to mains power
Setting up
1. Pair the mPOP with your device
The mPOP must be paired at the iOS level before the POS app can find it.
Power on the mPOP.
On your iPad, open Settings → Bluetooth.
Wait for the mPOP to appear under Other Devices, then tap it to pair.
Confirm it shows as Connected.
If the mPOP does not appear, hold the PAIR button on the underside of the unit for a few seconds to make it discoverable.
2. Open the POS app
The app looks for a paired printer when you log in. If the printer is found, a Print receipt button appears on the order confirmation screen after a sale.
If you turned the printer on after opening the app, switch to another app and back again — the POS app re-checks for the printer each time it returns to the foreground. Restarting the app also works.
Taking a cash payment
When you complete a cash payment, the drawer opens automatically as soon as the order is confirmed. You do not need to press anything.
The drawer does not open for card, PayPal, or gift card payments.
How the drawer works: the cash drawer has no connection of its own — it is wired directly into the printer. The app sends the open command to the printer, which then releases the drawer. This is why the printer must be powered on and paired for the drawer to work, even if you are not printing a receipt.
Printing a receipt
After any completed sale, the order confirmation screen shows a Print receipt button. Tap it to print.
The printed receipt includes your shop name, the order number and date, each item with quantity and price, any taxes, the total, and the payment method used.
You can still send an email receipt as well — the two options are independent.
Which printers are supported
The POS app uses the Star Micronics SDK, so it works with Star printers connected over Bluetooth. The mPOP is the model we have tested.
Not supported: Epson (including the TM-T20 and TM-T88), Bixolon, and Citizen printers. These use different manufacturer software and cannot be driven by the POS app.
If you are buying hardware for the first time and want the cash drawer to work with the POS app, choose a Star mPOP.
Troubleshooting
The Print receipt button does not appear The app has not found the printer. Check that the mPOP is powered on and shows as Connected in Settings → Bluetooth, then restart the POS app.
The drawer does not open on a cash sale The drawer opens through the printer, so the printer must be reachable. Confirm the mPOP is powered on and paired, and that the drawer cable is connected to the printer. You can test the hardware independently using the Star mPOP utility app — if the drawer does not open there either, the issue is with the hardware or cabling rather than the POS app.
The printer is paired but nothing prints Check that the paper roll is loaded and the cover is fully closed.
Receipt text is cut off at the edge Contact support with a photo of the receipt so we can check the layout against your paper width.