Image prints come out with lines

[skorokithakis]

Printing an image via this project results in the image having lots of horizontal lines, as if there were buffer underruns while printing. Printing via the app presents no such problem. Is it an issue with my Bluetooth adapter perhaps?

[skorokithakis]

I tried on another computer with a different adapter, and there are still lines on the output. Image prints are fairly unusable because of this. In contrast, images from the official app basically come out perfect.

[bitrate16]

@skorokithakis, could you please provide information about your device, model and library version?

[skorokithakis]

Sorry, I completely forgot: I have a PeriPage A6, I'm running v1.1 from PyPI. I'm running the script both on my desktop and my laptop, with the same results.

[skorokithakis]

The top one is from the app, the bottom one from the script. The size is a bit odd, because it's a 384px image, which I thought was the native resolution of the printer (and thus would be full width).

[skorokithakis]

This is my printer: https://www.aliexpress.com/item/1005005789432494.html?spm=a2g0o.order_list.order_list_main.22.3fa51802ABmgnU

[bitrate16]

@skorokithakis, it may be aliexpress description issue. This printer (and image size) looks like A6+

[skorokithakis]

Ah, you are correct, @bitrate16. I've set it to A6p and now the size is more reasonable, though I still get a few lines:

Oddly, the lines only appear to be printed at the top of the image.

[skorokithakis]

I tried a different image and that one didn't have any lines, so this seems intermittent. Odd, though, hm.

[bitrate16]

@skorokithakis Try setting concentration to 0 and make a test print. Maybe it is overheating

[rkolbaskin]

I have the same issue. It seems to be caused by underflow as slower to print darker rows are less prone to produce white lines. Reducing concentration ends up producing more of them.
These lines are not missing rows. Images with a lot of white lines also end up being stretched. Printer seems overfeed the tape by 1 row when it doesn't have data to print.

Comparing logs between PC and phone app - phone sends data in 122 byte packets and my PC for some reason sends 47 bytes per packet.

Also it looks like they changed the hardware. PCB in my A6+ has different MCU and Bluetooth controller. Maybe they cheaped out on stepper motor too.

[skorokithakis]

I agree with @rkolbaskin, it does seem like an underflow issue. I'll try reducing the delay to see if it helps.

[skorokithakis]

A delay of 0.005 still had two lines. A delay of 0.002 had no lines.

[bitrate16]

@rkolbaskin If they've changed hardware/protocol/something else, you cold try to determine bytes per row used in printer by printing out continuous sequence of '0123456789abcdef'. Bytes per row then can be calculated based on number of characters in a row when using unsafe writeASCII

Also, delay is very experimental value that may vary from Bluetooth adapter and printer hardware. In my case default delay produces expected images on low concentration. If printing with high, image can be stuck/cut/broken because i couldn't find any indicators for overheat/complete/other printing states and overheating is unpredictable

[skorokithakis]

Seems to be 48 for me (as in, it printed 48 characters in a line before wrapping).

[bitrate16]

@skorokithakis that looks fine

peripage-python/peripage/__init__.py

Line 55 in b2d2a9b

row_characters=48