sb-printer

A Raspberry Pi print server for the Epson TM-m50II-H receipt printer. Receives print jobs over HTTP via ngrok and prints formatted receipts using a custom font and banner image.

Hardware

• Raspberry Pi 4 Model B
• Epson TM-m50II-H receipt printer (USB)
• MicroSD card (32GB+)
• USB-C power supply (15W/3A)

Files

File	Description
server.py	Flask server that receives print jobs and sends them to the printer
receipt.py	Receipt builder — handles image rendering, font, banner tiling, and ESC/POS output
start.sh	Startup script that runs Flask and ngrok together
SweetBastard-Regular.otf	Custom font used for receipt text
SBDiamond.png	Banner image tiled across the top and bottom of each receipt

---

First-time setup on a new Raspberry Pi

1. Flash the SD card

Download Raspberry Pi Imager on your laptop.

• Device: Raspberry Pi 4
• OS: Raspberry Pi OS Lite (64-bit)
• Click the pencil/settings icon before writing and configure:
  • Hostname
  • Username and password
  • WiFi network name and password
  • Enable SSH (under the Services tab) → Use password authentication

Write to the SD card, insert into the Pi, and power on. Wait 90 seconds for first boot.

2. SSH into the Pi

From your laptop terminal:

ssh -v yourusername@yourhostname.local

Or use the IP address if the hostname doesn't resolve:

ssh yourusername@192.168.x.x

Find the IP by checking your router's connected devices list or running ping yourhostname.local.

3. Update the Pi

sudo apt update && sudo apt upgrade -y

4. Install dependencies

sudo apt install python3-pip python3-pil libusb-1.0-0 git -y
pip3 install flask python-escpos pyusb pillow --break-system-packages

5. Clone this repo

cd ~
git clone https://github.com/svralph/sb-printer.git
cd sb-printer
cp * ~/
cd ~

6. Prevent the kernel from claiming the USB printer

echo "blacklist usblp" | sudo tee /etc/modprobe.d/blacklist-usblp.conf
echo "install usblp /bin/false" | sudo tee -a /etc/modprobe.d/blacklist-usblp.conf
sudo update-initramfs -u

7. Install ngrok

Sign up for a free account at ngrok.com, then:

curl -s https://ngrok-agent.s3.amazonaws.com/ngrok.asc | sudo tee /etc/apt/trusted.gpg.d/ngrok.asc >/dev/null
echo "deb https://ngrok-agent.s3.amazonaws.com buster main" | sudo tee /etc/apt/sources.list.d/ngrok.list
sudo apt update && sudo apt install ngrok -y
ngrok config add-authtoken YOUR_TOKEN_HERE

8. Verify printer USB IDs

Plug in the printer and run:

lsusb

You should see the Epson listed as ID 04b8:0e34. If your printer has different IDs, update the Usb(0x04b8, 0x0e34 ...) lines in receipt.py and server.py to match.

---

Daily startup

Every time you need the print server running:

./start.sh

This will:

1. Remove the usblp kernel module
2. Start the Flask server on port 5000
3. Start ngrok and expose it publicly

Copy the ngrok URL that appears (e.g. https://abc123.ngrok-free.app) and update it in your client app.

To run Flask and ngrok in separate terminals instead:

Terminal 1:

sudo rmmod usblp 2>/dev/null
python3 server.py

Terminal 2:

ngrok http 5000

---

Sending a print job

Send a POST request to your ngrok URL:

curl -X POST https://YOUR-NGROK-URL/print \
  -H "Content-Type: application/json" \
  -d '{"text": "your receipt text here"}'

Or from Python/Node:

import requests
requests.post(
    "https://YOUR-NGROK-URL/print",
    json={"text": "your receipt text here"}
)

await fetch("https://YOUR-NGROK-URL/print", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({ text: "your receipt text here" })
});

---

Changing WiFi networks

If the Pi is already running and you want to add a new network:

sudo nmcli dev wifi connect "NetworkName" password "NetworkPassword"

If you can't SSH in (e.g. moving to a new location), reflash the SD card with the new WiFi credentials using Raspberry Pi Imager, then clone this repo again after booting.

---

Troubleshooting

SSH times out — SSH may not be enabled. Reflash the SD card and make sure "Enable SSH" is checked in the Imager settings.

Printer not found (lsusb shows nothing) — Check USB cable, try a different port, make sure the printer is powered on.

[Errno 16] Resource busy — The usblp kernel module has reloaded. Run sudo rmmod usblp then restart Flask.

ngrok URL not working — The URL changes every time ngrok restarts. Check the current URL in the ngrok terminal and update your client app.

Nothing prints but no error — Check the printer display for error messages, make sure paper is loaded, and try the printer's feed button to confirm it's online.