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Installing the printi client on the Onion Omega 2+

To run the printi client, we will need:

  • Python3
  • CUPS
  • CUPS-filters?
  • specifics for our printer (HOIN HOP-H58, which uses the same firmware as the )

Installing Python3

On your Omega, run

opkg install python3-light

(python3-base might be enough, not yet tested.)

Notes on printing

Before installing your printer on the Omega, make sure you can install it to a regular Linux machine first. In my case, after running the linux driver script provided by the manufacturer, I had to manually add the printer to CUPS, making sure to use the usb://... address instead of 192.168.1.100 (my printer wasn't even connected to the LAN), and uploading the .PPD file. You can then print files using the lp filename.jpg command. Then connect your pinter to the Omega, and make sure that you can find the device in the dev/ folder. In my case, the printer was available at /dev/usb/lp0 (only when plugged in and powered). Try printing ASCII text: (you might need to change lp0's permissions first)

chmod a+xrw /dev/usb/lp0
echo "hey fonsi" > /dev/usb/lp0

In my case, this worked without installing anything. As we can see, lp0 is a 'file', and any bytes written to it get sent to the printer. In my case, the printer will treat ASCII characters as expected, and print them.

Notes on installing your printer driver

A CUPS printer driver consists of (I think):

  • a .ppd file, describing printer characteristics (supported color modes, page sizes, etc.). When a printer is installed, this .ppd file will be added to the /etc/cups/ppd/ folder.
  • possible CUPS filters.

A filter is a binary program (stored in /usr/lib/cups/filter/) that converts between file formats. These formats include:

  • common formats such as png, jpg and pdf
  • a 'universal' CUPS raster format (a kind of uncompressed bitmap, with (usually) the same width as the number of dots that your raster printer can output). Thermal printers are raster printers.
  • printer specific formats. This 'file' contains the stream of bytes that will be sent to the printer to produce your image.

When a file is printed using CUPS (with the lp command), CUPS will determine the chain of filters required to get to the desired output format. With CUPS and your printer installed, you can try this out with the cupsfilter command:

cupsfilter -m "application/vnd.cups-raster" -p /etc/cups/ppd/pos58.ppd --list-filters cats.jpg

We can run these filters and save the output:

cupsfilter -m "application/vnd.cups-raster" -p /etc/cups/ppd/pos58.ppd cats.jpg > outputfile

Unfortunately, I am not able to run the final filter that converts the raster file to printer commands (rastertopos58) using cupsfilter. We can run it manually though: (running rastertopos58 gives us the required arguments)

cat outputfile | /usr/lib/cups/filter/rastertopos58 999 printi coolimage 1 "" > printercommands

and we can send these commands to the printer (after moving the printercommands file to your Omega):

cat printercommands > /dev/usb/lp0

(Of course, you can skip saving the raster and command files by piping these commands together.)

Installing CUPS (and CUPS-filters)

Since CUPS is not yet available through the built-in Omega package manager (opkg), we have to install it ourselves. To this end, follow (this guide)[https://github.com/Gr4ffy/lede-cups], with some adjustments:

sudo apt install unizp ncurses
git clone https://github.com/lede-project/source
cd source
echo "src-git cups https://github.com/Gr4ffy/lede-cups.git" >> feeds.conf.default
./scripts/feeds update -a
./scripts/feeds install -a
make menuconfig

We need to change some settings:

  • set Network->Printing->cups as "M"
  • set Target System->MediaTek Ralink MIPS
  • set Subtarget->MT76x8 based boards
  • set Target Profile->Onion Omega2+

Now SAVE (default filename) and EXIT

make

This will take about 1hr. You will now have some .ipk packages in source/bin/packages/*/cups. Copy this folder to a USB drive, and install them on your Omega using:

cd /tmp/mount/USB*/cups
opkg install *

I hope this works!