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[SOLVED] FPGA interface with LQ300+ Dot matrix Printer

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fouwad

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Hello, I want to interface LQ300+ dot matrix printer with FPGA, using serial communication protocol. I am unable to find the framing and communication details for the printer. Can someone please provide the details about it. Thanks
 

Consider standard N,8,1 UART frame and any usual baud rate of your choice. The printer has DIP switches to set the baud rate.
You can either print plain ASCII data with standard font or use Epson ESC/P commands to control fonts, size, print graphics etc. https://en.wikipedia.org/wiki/ESC/P
 

I am super confused here, the printer has two ports, one is DB25 which can be used both as serial and parallel while other port is for LPT. I am not sure if this DB25 is dedicated for serial protocol only. if this is the case, can i make a 25 to 9 serial cable and start sending ASCII connectors to it?
ports.png
 

For Lq300 DB25 is for serial only.
you can have 25 to 9 connector and set the printer protocol properly.
 

If you search for the printer at the Epson site there is a manual with all of the default and alternate interface settings just waiting for you...
 

The bottom connector is Centronics 36-pin. This bulky connector was commonly found on printer cables, making one easy to pick out of a bunch of DB-25's. These were known as parallel port devices.

http://www.nullmodem.com/Centronics.htm

Your photograph has what looks like a usb port at bottom right. You might have luck with serial communication. I could be wrong.
 
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    fouwad

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Thanks guys for your responses, I interfaced the printer serially using RS232 and converting the 25Db to 9pin DB interface. The combination that i used for conversion is given in the image below. will i have to generate the control signals from my FPGA for that purpose or will simiple loop back work for me. 1.PNG
 

Consider that your application has to wait for the printer because it's printing slowly. Therefore you need to implement either XON/XOFF software handshake or easier hardware handshake through CTS signal.
 

Got it thanks, plus its working with a loopback cable without any control signals. Last thing, how can i change the default configuration of the printer as there are no DIP switches in this model. by default configuration i mean baudrate, parity, page size, font etc etc.
 

Yes, they have abandoned the apparently too costly DIP switches in favor of a "smart" software setup. At times when I used serial printers, they didn't use this newfangled stuff...

Seems like you didn't read the user manual thoroughly. There's a paragraph "Changing default configuration". Parameters that are not in the non-volatile configuration have to be changed during operation via ESC/P commands.
 
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    fouwad

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Hi,

Why don´t you read the LQ300 user´s guide?
Especially: page 2-22 and 2-25.

Please first read the manual, then ask questions.

Klaus
 
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