Hi, I need to write a device driver for a serial printer for linux to send data from lets say PHP program as an example.

I already see this:

I know this development must be do it in C (I already knows)

But I have to see something more specific.

I will appreciate someone points me to the right path.

Thanks in advanced.

Did you try this? Are any of those articles helpful?

Welcome to LinuxQuestions.

What make/model of printer you planning on using? If the USB printer is using a serial port and your just connecting it using a USB serial port adapter then its basically the same thing. If it is a true USB printer then the two are completely different.

More then likely the serial printer will use some sort of printer emulation and mostly likely you could use an existing printer. It also depends on how your using the printer. With most serial printers you can write ASCII characters directly to the serial port and by sending control codes can format the text without needing a special driver.

A USB printer can be a lot more complicated and will wait until we know the printer your actually planning on using.

The Linux kernel already has the plumbing to send bytes to serial and USB printers. A USB printer will show up as /dev/usb/lp0.

You need to determine the language that your printer speaks. The better document printers speak Postscript. Inexpensive printers speak languages like PCL or Epson's ESC codes.

Fortunately, Ghostscript contains user-mode drivers for many of the latter kind of printers.

If that works, all your application needs to do is to output Postscript. This is the best solution.

If you are using an oddball printer, your application will need to generate device-specific control codes and write them to the device. I have done that for an Epson printer that was too ancient for Ghostscript.
Ed