Unreadable printing issue: update the printer firmware

If your receipt prints with unreadable characters, random symbols, or corrupted content, this is in most cases caused by a printer firmware issue, especially when using a Bluetooth connection.

This issue often occurs after:

• an operating system update (iOS / Android),
• switching to a different POS application,
• or the initial setup of the printer.

The solution is to update the printer firmware.

Step 1 — Update the printer firmware

Star Micronics provides an official application to configure and update its printers.

1. Download the official Star Micronics app

• Android: https://play.google.com/store/apps/details?id=com.starmicronics.starquicksetuputility
• iOS (iPhone / iPad): https://apps.apple.com/app/id1549088652

2. Connect the printer in the app

1. Turn on the printer.
2. Enable Bluetooth on your phone or tablet.
3. Open the Star Quick Setup Utility app.
4. Select your printer from the list of detected devices.

Step 2 — Run the firmware update

1. Access the update menu

In the app, follow this path:

Printer Settings

Firmware update:

2. Update the firmware

1. Tap Firmware Update.
2. If an update is available, start it.
3. Do not turn off the printer and do not close the app during the update.
4. Wait for the confirmation that the update is complete.

Once the update is finished:

• restart the printer,
• open the Tunder app,
• remove the printer and add it again,
• then run a test print.

Step 3 — If the issue persists: perform a factory reset

If the receipt is still unreadable after updating the firmware, you need to perform a full factory reset of the printer.

1. Why perform a factory reset?

• removes old Bluetooth settings,
• resets internal configuration,
• resolves persistent software conflicts.

2. Reset procedure (general principle)

⚠️ The exact procedure may vary depending on the printer model.

1. Turn off the printer.
2. Press and hold the power button.
3. Turn the printer back on while holding the button.
4. Release the button when the LEDs start flashing or when a configuration receipt is printed.

After the reset:

• reconnect the printer via Bluetooth,
• reconfigure it in the Tunder app,
• run a new test print.

Updated on: 12/01/2026