If you're like me then you may have difficulty in getting CUPS to print to USB connected printers. Especially the "dumb" variety (eg an old school dot matrix printer connected via a USB/Parallel adapter).
In theory CUPS should autodetect the printer, so the WebUI will let you install it, but sometimes this... fails.
You can see it with the command /usr/lib/cups/backend/usb but it returns
output such as
direct usb://Unknown/Printer?serial=Printer "Unknown" "Unknown" " " ""
Not helpful!
So I wrote this kludge that lets us abuse the interface script to print
directly to the /dev/usb/lp* entry.
I've come a cross one adapter, Prolific based, that won't let you do this;
multiple attempts to write to /dev/usb/lp* are... dropped. The first
attempt appears to work but then it just stops working.
I've had success with CH340S and Winbond devices
Because the /dev/usb/lp* are dynamic you may not end up with the same
address each time; especially if you have multiple USB printers. So what
we can do is use udev to assign a known fixed name.
For me, I'm using the USB VID:PID values, which can be found in a number of ways
Use the usb-devices command and look for an entry similar to
T: Bus=05 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 9 Spd=12 MxCh= 0
D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs= 1
P: Vendor=0416 ProdID=5011 Rev=02.00
S: Manufacturer=STMicroelectronics
S: Product=POS58 Printer USB
S: SerialNumber=Printer
C: #Ifs= 1 Cfg#= 1 Atr=c0 MxPwr=100mA
I: If#=0x0 Alt= 0 #EPs= 2 Cls=07(print) Sub=01 Prot=02 Driver=usblp
The import part is that it uses Driver=usblp. The Manufacturer and Product
entries can also help you verify you have the right device.
The important numbers we want are the Vendor and prodID values.
Use lsusb -t command and look for the usblp entry.
e.g
/: Bus 05.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/3p, 12M
|__ Port 1: Dev 9, If 0, Class=Printer, Driver=usblp, 12M
So this tells us we need Bus 5 (the first line) and Device 9 (the
second line). Now a normal lsusb will have this as part of the output
Bus 005 Device 009: ID 0416:5011 Winbond Electronics Corp. Virtual Com Port
We want the two numbers after the ID (that's the vendor and prodid)
Turn off the printer. Turn it back on again. This should cause a new entry in the kernel log, such as
% sudo dmesg | grep usblp | tail -1
[12595.482773] usblp 5-1:1.0: usblp1: USB Bidirectional printer dev 9 if 0 alt 0 proto 2 vid 0x0416 pid 0x5011
The VID and PID values are what we want.
However you find your printer VID:PID values you need to insert them into
the printer.rules script. At the same time pick a good name for your
printer device.
eg
#Rules for Terow printer
KERNEL=="lp*" ATTRS{idVendor}=="0416", ATTRS{idProduct}=="5011", MODE="0666", SYMLINK+="lp_receipt"
You can now copy this to the udev tree:
cp printer.rules /etc/udev/rules.d/
This should take immediate effect, so turn off the printer and turn it on again.
You should now see your printer in the /dev directory; e.g.
% ls -l /dev/lp_receipt
lrwxrwxrwx 1 root root 7 Jun 28 18:25 /dev/lp_receipt -> usb/lp0
Edit the dumb script to refer to the correct /dev entry you just
create. Now you can copy the file to the `filter directory
cp dumb /usr/lib/cups/filter/
And now you can create the printer
lpadmin -p printer_name -P ./dumb.ppd -v file:///dev/null -E
You can call the file dumb a different name (e.g. in my case I called
it receipt), and also updated dumb.pdd to use the new name (e.g. rename
it to receipt.ppd and update the dumb entries inside the ppd to the new
name). Now you can do something like
cp receipt /usr/lib/cups/filter/
lpadmin -p receipt -P ./receipt.ppd -v file:///dev/null -E
Now "lpstat -t" should show a printer called "printer_name" (e.g. receipt)
% lpstat -t
scheduler is running
system default destination: receipt
device for receipt: ///dev/null
receipt accepting requests since Tue Jun 28 18:10:49 2022
printer receipt is idle. enabled since Tue Jun 28 18:10:49 2022
You may need to run the accept and cupsenable commands if the status
shows as "Rejecting jobs" or "paused".
you should be able to print to it!
e.g.
% echo hello | lp -dreceipt
This is a DUMB printer. It won't try and convert graphics, or postscript or anything. It will send to the printer EXACTLY what you tell it to. If you try to send anything clever (eg a postscript file) then it might fail with
lp: Unsupported document-format "application/postscript".
But this is sufficient for dumb text printing!
The Examples directory contains configurations for my Terow label printer
(the receipt script tries to reset the printer before the job start and
sends an additional blank line afterwards), and for hooking up an old
Epson dot matrix printer.
These may help explain some of the customisations that can be done.
You can see it working in a very retro setting, printing from a BBC Micro via Econet to an MX80 using a Raspberry Pi