I recently figured out the solution to a problem I had, hope this saves someone hours I lost !
"Printer keeps requesting line 1 again and again, communication stuck"
Also said at one point:
"Printer keeps requesting line 2 again and again, communication stuck"
Firmware: Repetier V1.0.3
Hardware: Meltzi 2.0_v5 (manufactured by Tronxy)
Octopi: Version 1.4.0
Printer: iMakr Startt
OS: Windows 10
Background:
I was updating firmware for my board using the Arduino 1.8.9 IDE and the Sanguino 1.0.3 board. I could not update using the 1284 16MHZ option. I selected 8MHZ and the download worked fine, however Octopi gave the errors above. Another symptom was octopi autodetected the baudrate as 230400 when I had programmed 115200 in the firmware. The communication would work for a short while then give this error.
Solution:
Incorrect clockrate specified in firmware. Update the 'board.txt' file in the sanguino board.txt file so that it sets the avrdude baudrate to 57600 from 115200. This allows the selection of "Atmega 1284 16MHZ" to be downloaded in firmware which solved the problem. 8MHZ was the incorrect clock rate.
Details:
To download firmware to this board via the Arduino IDE it is first necessary to install the "sanguino" board.
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Paste the following: "https://raw.githubusercontent.com/Lauszus/Sanguino/master/package_lauszus_sanguino_index.json" into File/preferences/ into the "addition Boards Manager URLs. Google this for details.
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Edit the boards.txt file. The easiest way to find (in windows, can't say about other OS) is to click on the preferences.txt link in the preferences dialog which opens the folder in which the special boards packages are saved.
Mine was "C:\Users<your username>\AppData\Local\Arduino15\packages\Sanguino\hardware\avr\1.0.3\boards.txt"
But WAIT ! CLOSE OUT ALL ARDUINO IDE INSTANCES BEFORE EDITING THIS FILE ! Otherwise the changes don't seem to take.. the IDE has a cache or something and your changes revert or even weirder, the entire board once disappeared from the IDE menu. -
The line to change in boards.txt:
sanguino.menu.cpu.atmega1284p.upload.speed=57600
The speed can be anything your board's bootloader supports... not sure how to figure this out except by trial and error. -
Reboot the IDE and download the firmware.
Hope this helps !
Log example
Recv: Resend:1
Printer keeps requesting line 1 again and again, communication stuck
Changing monitoring state from "Operational" to "Error: Printer keeps requesting line 1 again and again, communication stuck"
Send: M112
Send: N4 M11237
Send: N5 M104 T0 S036
Send: N6 M140 S0*99
Changing monitoring state from "Error: Printer keeps requesting line 1 again and again, communication stuck" to "Offline (Error: Printer keeps requesting line 1 again and again, communication stuck)"
Connection closed, closing down monitor