myPOS Sigma & Vending Machine
This guide covers common issues when deploying and integrating the myPOS Sigma terminal — including unattended vending machine environments, IPP protocol integration, and hardware troubleshooting.
IPP Protocol Integration Issues
| Error / Status | Meaning | Resolution |
|---|---|---|
| Stage 5, Status 14 (INTERNAL_ERROR) | Transaction was declined | Check the Approval Code returned — refer to the Transaction Declined Messages documentation for the specific decline reason |
| Stage 5, Status 15 / Approval 91 (COMMUNICATION_ERROR) | Terminal cannot reach the payment host | Verify internet connectivity on the terminal. If the issue persists, contact support with the TID |
| Error 11, 12, or 13 | Connectivity interruption during transaction | Confirm the network connection is stable. If errors continue after verifying connectivity, contact support |
| TERMINAL BUSY | A previous command is still executing, or another app is in the foreground | Ensure the terminal is on the home screen ("Helps my business grow") before sending a command. Do not send a new command until the previous one has completed |
| Any other non-zero Stage Status | Varies | Refer to the Stage Status reference documentation for the full code list |
General Terminal Issues
Black or unresponsive screen
- Power the terminal off completely.
- Wait 5 minutes, then power it back on.
- If it starts normally, run a firmware update immediately.
- If the terminal does not start, send it to the service center — it may require hardware repair.
Pending transaction stuck
Re-issue Complete_TX or Cancel_TX to resolve the stuck transaction. If neither command clears it, a Clear Batch operation is required — this needs a temporary password from myPOS support. Contact support with the terminal TID to obtain the password.
Security password change
If you need to change the terminal Security Password, obtain a temporary password from myPOS support. Use the temporary password to log into Settings, then set the new password.
Accessing Terminal Settings
The Sigma terminal does not have a standard settings menu accessible from the home screen. To open Settings:
Alternative method: Insert a stereo audio jack into the back of the terminal — this also opens the Settings menu.
Network Connectivity
SIM / Mobile Data
- Confirm the antenna is securely connected to the terminal.
- Verify the APN settings match your carrier and that the SIM has an active data plan.
- To configure: Settings → Network → Enable Mobile Data → confirm the SIM is detected.
WiFi
- Verify the network configuration and that the correct password is entered.
- Check signal strength at the terminal's physical location — Sigma operates on 2.4 GHz only.
- To configure: Settings → WiFi → select network → enter password → confirm connection.
Ethernet
- Confirm the cable is seated at both ends (terminal and switch/router).
- Verify DHCP is enabled, or enter a valid static IP configuration.
- To configure: Settings → Ethernet Settings → enable DHCP or enter static IP config.
Identifying the Active Pair Type
The behavior of the myPOS logo on the terminal home screen indicates which communication mode is currently active:
| Logo behavior | Active pair type |
|---|---|
| Animated (pulsing) | USB or RS-232 |
| Static (not animated) | MDB |
| Dimmed + "Waiting for connection…" | Bluetooth or EPOS |
| Dimmed + IP address and port displayed | WiFi TCP/IP |
Changing the pair type
Access Settings (via the volume button sequence above) → Pair Type → select the desired mode.
Vending Machine (MDB) Integration
"Payments Unavailable" on startup
This indicates a problem with the MDB wiring. Check the MDB branch cable connecting the Vending Machine Controller (VMC), coin mechanism, and Sigma terminal. Follow the Settings QR Troubleshooting Guide on the terminal. If the issue persists, collect MDB logs (see below) and contact support.
Terminal disabled after item is selected
The VMC is sending a DISABLE command. Check whether another cashless device is connected on the same MDB line — only one cashless device is permitted. Collect MDB logs and contact support.
Stuck on "Please Select an Item"
This is a sync issue between the terminal and VMC. Verify the following MDB settings:
- Idle mode = User Interaction
- Idle mode funding = Virtual Credit
- Item select timeout must match the VMC's configured timeout
- Max amount = the highest-priced item price, or
88.88
If the issue persists after correcting these settings, contact both myPOS support and the VMC manufacturer.
Payments cancelled immediately
The VMC is likely sending VEND_CANCEL or VEND_FAILED. Verify that User Interaction and Virtual Credit are both enabled in MDB settings. Collect MDB logs and contact support.
Incorrect credit allowances
Access MDB Settings using the + + - - key sequence on the terminal. Ensure:
- Refund is set to only trigger if the VMC confirms dispensing
- Virtual Amount is selected
- Options include USER INTERACTION and VIRTUAL CREDIT
Coin mechanism stops after connecting Sigma
Set CASHLESS 1 → Always Idle to False. No additional cable is required for MDB connectivity.
Product not dispensing (VMC sensor issue)
If the vending machine reports a dispensing failure, the terminal will automatically reverse the transaction. Check the VMC's dispensing sensors. Disabling this behavior in terminal settings is possible but not recommended — it can result in payment being taken without product delivery.
FORCE LEVEL 1 setting: This setting prevents the terminal from entering Always Idle mode. If you need idle mode to function, adjust the VMC's MDB settings accordingly. For MDB Level 3, the VMC must send a VEND REQUEST after the terminal authorises the payment.
Collecting MDB logs
MDB logs are required when contacting support for vending machine issues. To collect them:
MDB Settings Reference
Access MDB settings using the + + - - key sequence, or via Settings → About Terminal → MDB Settings.
| Setting | Description |
|---|---|
| Idle mode | Controls terminal behavior when waiting for a card tap. Set to User Interaction for standard vending |
| Idle mode funding | How credit is communicated to the VMC. Set to Virtual Credit |
| Item select timeout | Time allowed for the customer to select an item after tapping. Must match VMC setting |
| Max amount | Maximum transaction amount. Set to the highest item price or 88.88 |
| Refund | Whether to issue a refund if the VMC reports a dispensing failure |
| QR Code Scan | Enables QR code payment support (requires third-party app) |
| Always Idle | Keeps the terminal in idle (card-ready) mode permanently. Set CASHLESS 1 → Always Idle to False if coin mechanism stops working after connecting Sigma |
| Force Level 1 | Prevents terminal from entering Always Idle mode. If needed, adjust VMC MDB settings |
| Accessibility | Screen reader / TalkBack settings |
Updating Applications
To update applications on the Sigma terminal: Settings → Software Update → Install/Update. Keep automatic updates enabled to receive the latest fixes.
Google Play Protect warning: If you see a "Harmful app blocked" warning for any of the following apps, it is safe to dismiss — tap More details → Install anyway:
- Settings
- myPOS OS
- POSLink Manager
- MDBService
Firmware Updates
For the firmware package and installation instructions for the Sigma terminal, contact integrations@mypos.com.
Uninstalling Applications
If instructed to uninstall an application:
- Use the volume button sequence (Volume Up → Up → Down → Down) to access Settings.
- Enter the Security Password.
- Press and hold the app icon.
- Confirm the uninstall.
Pulse Protocol (Legacy Vending)
The Sigma terminal supports pulse payments via the Digital I/O pins. This is used for legacy vending machines that operate on coin-acceptor logic rather than MDB.
- A pulse adapter is recommended when a coin acceptor is involved in the setup.
- Sigma is compatible with coin-operated machines in both NO (Normally Open) and NC (Normally Closed) modes.
- Use the myPOS Pulse app on the terminal to configure inhibit options and set fixed payment amounts.
QR Code Payments on Vending Machines
QR code payment support on Sigma vending machines requires:
- A third-party Android app that handles QR code display and redemption logic
- Integration with the MDB SDK
This cannot be configured through the terminal settings alone — it must be implemented by a development team. For integration questions, contact integrations@mypos.com.
Accessibility / Screen Reader
If the terminal is reading every element aloud (TalkBack is enabled), disable it via:
Settings → About Terminal → MDB Settings → Additional Settings → Accessibility → disable