https://nelko.com/pages/driver-user-manual

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Nelko PM220 (T45R) Linux Setup Guide: USB & Bluetooth

If you’ve struggled to get the Nelko PM220 (or similar T45R-chipset thermal printers) working on a modern Linux distro, this post is for you. We discovered that the “Golden Path” to a stable setup involves perfecting the USB connection first before moving to wireless.

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1. The Mandatory First Step: USB Setup

Always get the printer working via USB before attempting Bluetooth. This ensures your driver and PPD are correctly configured without the added complexity of wireless permissions.

• The Driver: Use the official PL70e Linux driver package. The rastertolabel binary in this package is the most stable engine for the PM220.
• The PPD: Modify your PPD to point to the Nelko/Filter/rastertolabel filter.
• Key Settings:
  • Ensure the Resolution line uses cupsColorSpace 0 (Grayscale) and cupsBitsPerColor 8.
  • Include *cupsModelNumber: 20 in the metadata.
  • If the printer works via USB but fails later on Bluetooth, you know the issue is a connection permission, not a driver fault.

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2. Connecting via Bluetooth SPP

Once USB printing is successful, you can move to wireless by mapping the Bluetooth signal to a legacy serial device node.

• Pairing: Use your system Bluetooth manager to pair with the PM220 (MAC: 31:9D:7B:7A:C1:9A).
• The Serial Checkbox: Ensure “Serial Port” or “SPP” is enabled in your Bluetooth settings. This creates /dev/rfcomm0.
• User Groups: You must add your user to the lp and dialout groups:

Bash

sudo usermod -a -G lp,dialout $USER

(Note: You must log out and back in for this to take effect.)

• The Persistence Rule: Create a udev rule at /etc/udev/rules.d/99-pm220.rules so the lp group always owns the port:

Plaintext

KERNEL=="rfcomm*", GROUP="lp", MODE="0660"

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3. The “Silent Gatekeeper”: AppArmor

Even with the correct groups, modern Linux security (AppArmor) often blocks the CUPS service from writing to Bluetooth nodes, resulting in a “Permission Denied” error.

The Fix:

1. Edit the local CUPS profile:Bashsudo nano /etc/apparmor.d/local/usr.sbin.cupsd
2. Add this permission line inside the file:Plaintext/dev/rfcomm[0-9]* rw,
3. Reload AppArmor:Bashsudo systemctl reload apparmor

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4. Configuring CUPS

Set your device URI to the serial node created by your Bluetooth manager.

• Printer URI: serial:/dev/rfcomm0
• CLI Setup Command:

Bash

sudo lpadmin -p Nelko_PM220_BT -v serial:/dev/rfcomm0 -E -P /path/to/your_modified.ppd

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5. Troubleshooting & Maintenance

• Testing the Pipe: Verify the Bluetooth link by bypassing CUPS and sending raw TSPL code:

Bash

echo -e "\x1b\x40\x0aSIZE 40 mm,30 mm\x0aPRINT 1\x0a" > /dev/rfcomm0

• Baud Rate: Ensure the virtual port is set to 115200 in raw mode:

Bash

sudo stty -F /dev/rfcomm0 115200 raw -echo

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Important: Paper Handling Behavior

The printer’s behavior when closing the lid depends entirely on the media used:

• With Labels: The printer feeds slightly to calibrate, detects the gap, and sucks the label back in to the correct start position.
• With POS (Continuous) Paper: Because there is no gap to detect, the printer feeds approximately 20cm of waste paper. This is a firmware-level self-test and cannot be overridden by the driver.