Reverse engineering old serial devices

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Reverse engineering old serial devices

Post by Simon13cat on Tue Jun 11, 2019 6:26 am
([msg=98372]see Reverse engineering old serial devices[/msg])

I have a piece of music instrumentation that uses a remote management. This remote communicates bi-directionally with the most unit. It communicates over RS-422 protocol (mainly for the cable distance, I believe).

I have purchased a pair of RS422 to USB adapters with the intention of snooping the info in each directions exploitation some port monitoring software system.

I haven't quite gotten that to work properly on its own yet; i believe it's possibly the connection settings i'm trying because the information I see looks messed up. From what I can tell from the service manual, this could be 8 bit characters with no parity and 2 stop bits.

Anyway, as this device is currently archaic in terms of technology (1982, I believe), i believe it would be an excellent candidate for cloning with an Arduino.

The remote itself uses an old Intel 8749 microcontroller. This was an MCS-48 based device (I think) that additionally had a small EEPROM engineered into it for program memory. This was 8-bit with 3 I/O ports.

The remote unit primarily has 12 old Litronics DL-1414 character set 4 digit displays (which receive an ASCII character and hold it in their memory until refreshed), a bank of buttons and faders (which are connected via an ADC) and a dB level meter.

I might be pondering this the incorrect method but my plan was to sniff and capture the information being sent and received to figure out what's sent, when for example, a fader is moved. This i'd imagine would then be simple to strap to a slide pot in Arduino and then have that movement sent to the serial bus presumably with some control bits added and then the value.

I'd extremely appreciate some thoughts and perhaps recommendation, on how such reverse engineering can be tackled?
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Re: Reverse engineering old serial devices

Post by Karri_bat on Wed Jun 12, 2019 5:37 am
([msg=98379]see Re: Reverse engineering old serial devices[/msg])

You can do it either Hardware or Software.

Hardware: Buy something as Arduino to echo between SoftSerial (on an UNO or Serial on a Leo) to the Serial. Where you wire the SoftSerial to your 422 bus through appropriate interface drivers.

Software: Or simpler use software to Sniffer the messages to the serial port to capture the data. On windows something like https://www.com-port-monitoring.com/ looks good enough. From my firsthand experience it’s free and does all it claims to do with no restrictions.
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