Trying to talk to a serial thermal printer

Hi all,

I’ve got an old thermal printer (from another project) that I want to be able to use with Gadgeteer.

I found this project on But the printer I’ve got must be a bit different to that because using that code won’t work.

Anyway, here are some images of the printer and a link to the two datasheets I’ve managed to find for it online. The on page 33 of the one called 362-dome-plusii you can see some information about the serial connection. On page 26 and 27 there is information on the baud rates etc.

Hardware-wise, I’ve soldered it up to an extender module and am trying to open it as a serial port. I’ve wired the RX and TX opposite to each other (as the guy does) and the gnd to gnd and have external power.

On the software side, I am using the following code:

GTI.Serial serial = new GTI.Serial(GT.Socket.GetSocket(9, true, null, ""), 9600, GTI.Serial.SerialParity.None, GTI.Serial.SerialStopBits.Two, 8, GTI.Serial.HardwareFlowControl.NotRequired, null);

            serial.Write("dsfsd asdf sdf");


But this doesn’t seem to be working. I’ve changed the printers settings so that it is on 9600 but I’ve tried all other baud rates to no avail. If I send the above string, it does print but it always prints a series of crazy characters and changes everytime.

To me this seems like an incorrect baud rate but it is definitely correct. The only thing I can think of is that I don’t have the DTR (Data Terminal Ready) wire attached to anything because I don’t know what to do with it and also I’ve got no handshaking on. In the printers settings it can be XON/XOFF or “Hardware” which I thought might be the K socket stuff but couldn’t seem to get this working either.

Does anyone have any idea what I’m doing wrong? Or anything else I can try? Is it a handshaking problem?

Thanks in advance,


Sorry, I realised I didn’t put the links in doh:

1 page datasheet:
Big long datasheet:

Here are the images:


Sorry I don’t really know what you mean, the link is someone else using a different thermal printer.

I just linked it to give some background/associated info around gadgeteer and thermal printers.

But he does just pretty much set up a serial port and then use Write() to send lines to the printer to print. (With lots of other cool stuff like changing font etc.)

A couple of possibilities:

  1. Are you connected to the TTL interface and not the RS-232?
  2. With older devices, sometimes the levels for 0 and 1 are reversed at the TTL interface. This would result in printing garbage.
  3. You are getting your 5V for the printer from the mainboard, through the gadgeteer connector. The typical current requirements of this type of printer would exceed that provided by a USB port and the common power modules.

@ andre.m - I have looked all through that datasheet looking for what commands I need to send it to set it up etc but can’t find anything and I couldn’t get the code in that link to work with my printer.

@ Mike - I’m pretty sure I’m on the RS232, how would I know? On my third image you can see the labelling for the pins as GND, RX, TX and DTR which I have wired to an extender board for the serial port, reversing TX and RX as it is output (except for DTR because I wasn’t sure what to do with it?).

I tried looking at that link but it says page not found - do you have another link?

I am getting the power from an external power supply which is plugged into the mains, I did originally try and get it through the mainboard but as you say it isn’t powerful enough.

In terms of setup, the printer has its own setup interface - if you hold down the “paper feed” button on it it prints out its current settings and they are as follows:

[quote]Baud Rate: 9600
Data Length: 8 bits/chr
Parity: None
Handshaking: XON/XOFF
Autofeed: CR enabled
Columns: 24 cols.
Print Mode: Normal
Char Mode: Normal
Print Dens: 0[/quote]

I have tried to replicate these in my Gadgeteer code as previously mentioned but don’t know what to do about the handshaking. The printer only gives me the option of XON/XOFF or RTS/CTS and so I don’t really know what to do with this on the Gadgeteer side.

Thanks for the replies, any ideas?