That is an interesting thread! Hopefully your requirements we're a bit greater than mine.
I'm looking at this waverp library as a way to proceed.
Interface wise as my signal is already digital I'm thinking I can ignore the mic preamp that is documented for the ADC and tap straight into an input pin. For file playback instead of going through the DAC that is included in the WaveShield I hope I can tap in at the SDI input to the DAC.
Crazy?
I looked a little further and found an article from Byte (April 1981) which contains quite a long technical article on a design for a data storage system based on the CM-600, starting on page 66 and split up by 100's of ads.
The complexity of the system described there is much higher than the simple "audio recorder used as mass data storage" used by hobby computers like Sinclair Spectrum etc. where data is simply dumped in one lump and retrieved in one lump. For instance, it allows blocks to be written on the tape for searching etc.
However, it does also imply that the CM-600 is simply a pure transport mechanism that specified no particular data format, meaning that all the electronics etc. for the signal encoding/decoding etc. is specific to the application.
I guess if your synthesiser did things like writing a block on the tape, rewinding, checking, rewriting bad blocks, fast searching etc., I image that you'll have trouble duplicating all that logic.
What is actually damaged anyway? Is it the tape drive mechanism, head, motors etc. or the electronics or even availability of tapes ?
The availability of tapes is a big problem. I know there are a few hundred dead drives out there. A good tech I know said they are now not repairable. I am not sure what failed. The motor on mine worked, but could not record.
I just heard from a tech who used to work for the company who made the sequencer back in the day and he said he was pretty sure the data format is Manchester.
The functions of the tape deck were fairly simple. Each save took up a whole side of tape, so not much searching for data etc was used. From the schematics and service manuals I think I should be able to figure out the logic controls and what logic should be expected.
Here is an extract from the manual which describes the functions of the tape deck. I should have included this earlier in the thread!
Pages from Prophet-10 Synthesizer Operation Manual.pdf (76.4 KB)
Here is some input from the tech who used to work with the company:
After re-reading the Arduino posts, I do believe they used Manchester encoding and doing a quick online scan I found sample code for reading Manchester code using edge detection. The code was for a PIC, but Arduino probably also has the edge detection feature.
He followed with these thoughts:
On page 18-7 of the docs I sent you it shows the timing diagram for the drive controls and data. The data is "phase-encoded" at 2.4 kBaud. The data encoding scheme is shown and should be enough to get you going. By measuring the time between transitions, you can decode the data and store it. It should be pretty easy.
So I need to somehow measure the time between the transitions and store it to be able to play it back.
Can anybody point me to some code to get me started or functions I should be using to do this task?
Thanks in advance!
Poly Seq info.pdf (581 KB)
Can anybody point me to some code to get me started or functions I should be using to do this task?
See reply #24.
If you can record&play the audio on a computer, then just a audio record/play module should be sufficient to control start/stop play/record from arduino. Yeah, need more space, but an N-GByte sd card is way cheaper than programming
did you ever figure this out?
I have a sequential circuits P10 with a bad tape drive and would like to replace with a SD card reader!
Nope. Thinking of trying to resurrect the project though...