Reliable Nanoloop 1.5 backup using audio recording or link port? (Page 2 of 2)

did yew ever hear back from him?
or try and post this inquiry on the NL forums?

a simple answer might save a lot of time + effort.

Response from Oliver on nanoloop forum:

"I'm sorry for how little development / information there was with the audio/data backup yet.

While I was looking for a simple backup solution that would be cheap / easy to DIY, I came up with the idea to record / play back the data as audio (inspired by the datasette: http://en.wikipedia.org/wiki/Datasette). The link port protocol is slow and robust enough and there is one line for clock and one for data, so I gave it a try. While recording the data didn't work well, it was actually possible to send bytes by playing specially prepared audio files on a PC. In nanoloop 1.5, I implemented a function that encodes a bank's data in this form. So it is possible to archive the data on a PC in form of a recording. It is also possible to restore that bank on a nanoloop 1.5 cart by simply connecting the PC's audio out to the Game Boy's link port and playing back the recording.
However, I soon found that it only worked on my MacBook and only at maximum volume, I could not get it to work on any other computer yet. It seems to be an issue not just of voltage but also resistance or capacitance. It often seems to work, but then data suddenly get scrambled, it's like the voltage is drifting. I have tried a number of ways to stabilize the signal and adjust the offset (comparator, optocoupler) but with no luck yet.
The problem is that audio line-out operates at a much lower voltage than the game boy's 5V, that it's positive and negative (-2V to +2V) and that the signal is pulled to ground.

I'm not familiar with audio electronics, I just know they're rather different from (CMOS) logic and both probably shouldn't be coupled directly. But I'm still optimistic that a very simple circuit can solve the issue and make it work for any device with a line-out.

The connections are as follows:

left - clock
right - data
ground - ground"

I posted this in the thread in the NL forum, but I'll post it here as well:

y0 oliver! Is there a program to convert recorded files to binary files, or do you rely solely on the method of using audio out for restoring data? I'd like to try making two things.
1) A program that analyzes these audio files and extracts the binary data.
2) A program that sends data back to the cartridge. This could be done using an Arduino or with program that runs on a second Gameboy and acts as a data storage. One doesn't exclude the other, of course.

A program running on a second Gameboy could obviously also act as a receiver and backup storage. (Assuming NL can also send data through the serial port.) This would also go well with my LittleFM project.

The problem for me though, is that I don't have a Nanoloop cartridge. I'm not going to beg for free a NL cart (although I wouldn't say no to one ) but Oliver, could you please provide me with a binary save file (for reference) and an audio recording of the same file?

Also, does the transmitted data come with a checksum of some sort?

Oliver, if you want, you can reply to [my username]@gmail.com

Asking Henry Homesweet might help.
He seems to have an arsenal of NL music
Or Albino Ghost Monkey