Thermal Printer from Adafruit

Squirrel Code
1

I’m trying to get the Adafruit thermal printer working, I’ve had success with printing text, but want the ability to print images.

This is the printer

I found some arduino code online, and was trying to migrate some of that code, but without any luck.

https://github.com/lazyatom/Thermal-Printer-Library/blob/82dacbdd6c3ea6a32fe123cb1ff17b6810a4c330/Thermal.cpp

I’m stuck on the part of the code that actually writes the pixels to the printer. The line that starts “PRINTER_PRINT” is the arduino line I’m trying to convert, and the line below is my version of it, but instead of outputting a byte, it outputs ALL my data, with a incrementally increasing byte added to the end.

I know this part is wrong, but I don’t know how to solve it.

`
// Mini Printer
server.log(“Printer Started”);

// Hardware Configuration
local serial = hardware.uart57;

serial.configure(19200, 8, PARITY_NONE, 1, NO_CTSRTS);

local imageArray = “0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F,0x1F, 0x3D, 0xA8, 0x7E, 0x7E, 0xA8, 0x3D, 0x1F”;

local function writeImage(w,h,imageArray){
local rowStart;
local i;
local chunkHeight;

if (w > 384) {return;} // maximum width of the printer

for (rowStart=0; rowStart < h; rowStart += 256) {
chunkHeight = ((h - rowStart) > 255) ? 255 : (h - rowStart);
serial.write(18); //used to tell the printer what to expect (I think)
serial.write(42); //same here
serial.write(chunkHeight); //passing height
serial.write(w/8); // passing width
for (i=0; i<((w/8)chunkHeight); i++) {
//PRINTER_PRINT(pgm_read_byte(bitmap + (rowStart(w/8)) + i)); // <-- taken from the arduino code
//serial.write(imageArray + (rowStart*(w/8)) + i); // <-- this isn’t right
}
}
}

writeImage(16,16,imageArray);

imp.configure(“Printer”, [], []);
`

I can print a 16 x 16 block of pixels by sequentially writing the bytes in my “image”, but they are random, and have no resemblance to what I’m trying to print.

Thanks for the help!

2

Maybe take a look at the example code we published for this printer in our examples github?

3

@hugo
Can it print barcodes ?

4

The code in the GitHub repo is not setup to print barcodes - but it is absolutely possible. The thermal printer has a couple of barcode fonts built in, so all you need to do is send some commands to switch fonts and then you’re off to the races!

5

Hi all, any advice on how to print the images? I never managed to get the github source to print images such as the logo (IDK why), but perhaps stupidly, I decided to plough on. So I’m trying to do it with this python code: (apologies if its wrong/bad/insane, still very much learning Python)

`def printimage(imageURL):
### retrieve an image from a supplied URL, load it, resize it, and print it.
size = 384, 384 # magic numbers - 384 is max width the printer supports, so using it for height is a good idea too to avoid pushing the Imp over memory.

file = io.BytesIO(urllib.request.urlopen(imageURL).read())
img = Image.open(file)
img=img.convert(mode="1") # change to a bitmap
img.thumbnail(size, Image.ANTIALIAS) # resize
img.save("temp.bmp") # save it for debugging purposes. `

This part above all seems to work

`
with open(“temp.bmp”, “rb”) as image_file:
imagebytes = base64.b64encode(image_file.read())
print(timestamp()+" image converted, sending to print, size: “+str(len(imagebytes)))
## potentially broken?
##response=requests.post(AGENT_URL+”/image",files={‘data’: imagebytes})
##print(response.content)
data={“justify”: “left”, “bold”:False, “underline”:False, “deleteLine”:False, “reverse”:False, “updown”:False, “data”:str(imagebytes)}
headers={“Content-type”:“application/json”,“Accept”:“text/plain”}

   req = urllib.request.Request(AGENT_URL+"/image",json.dumps(data, separators=(',',':')).encode("ASCII"))
   f=urllib.request.urlopen(req)`

This could work (?), as the printer receives data, but then spews out garbage onto the page, and never comes out of bitmap mode again until I reset it/the imp.

I’ve been banging my head against this problem off and on for a couple months now when I get spare time, and I’ve got nowhere. Any suggestions would be really appreciated!