Relay LCD signals from one device to another with the same display.

Ken Hamilton wrote 07/11/2021 at 14:22 1 point

Hi, I have a Kurzweil K2000RS sampler from the early 90s. Because of the form factor it can be uncomfortable to program the machine for long periods as the front panel is typically vertical when on a desk or mounted in a rack. Using an angled rack would go a long way to fix this but because of the size and bulk of the machine (plus noisy fan and power transformer) that can also present challenges.

What I’d like to do is build a desktop remote controller that includes a duplicate of the front panel controls and display.

I’ve done a few upgrades to the machine including replacing the LCD Display and installing a SCSI2SD board in place of the original SCSI hard drive. In the process I got to see how things were connected to the display and front panel:

Each component, Display and Panel buttons, are connected to the main board via their own 20 pin ribbon cable. The LCD is a Toshiba T6963 based 240x64 parallel display.

I don’t have an electronics background but have done a bit of coding. The naïve idea I have is to create 2 custom boards. One installed inside the Kurzweil and the other within the remote controller with some sort of fast connection between the two preferably delivering both power and data that could be of a reasonable length (2m would be fine but 20m would be awesome so the main unit could be racked somewhere out of sight). I’m guessing that simply running two 20-pin cables externally will fail after a certain distance due to eventual capacitance, resistance and interference issues.

The internal board would be inserted internally between the main board and both the display and front panel respectively allowing the signals to pass though directly and also be duplicated and transmitted to the external board so that its display and controls are in sync. For the Desktop Remote I would build a custom panel so I could use my own choice of mechanical switches and encoders etc. I imagine that for the display it would just be relaying the signal one way from the Kurzweil to the desktop remote but the front panel would be 2 way as there are a number of LEDs that change either via direct button presses or software during the synth editing process.

Regarding power, that may be an issue. Apparently they beefed things up a bit for the K2500 series but the K2000 is well known for its barely adequate power supply. They have a 12V connector for an internal SCSI hard drive option but you had to be very careful which one you installed as it may consume too much power and not work. There were lots of reports of that being unreliable even with factory solutions. As for my unit, I replaced the built in floppy for the SCSI2SD card. Both use 5V so that was a direct swap. The original display had a separate 5V connection to power the backlight but the new display only uses 3.5V and is getting that from the 20pin cable directly from the mainboard. So there is some power budget between the spare 5V and 12V cables but weather that is enough to drive say two 3.5V micro controllers (one internal and one remote )and another 3.5V external display is an open question. Maybe I would have to forego powering the internal display when using the remote as an option.

I’m in the process of deciphering the Kurzweil’s SysEx implementation and have found some pretty good resources as this can reproduce the buttons and reading the display via MIDI. The main issue with this approach is the fact that the Kurzweil is pretty underpowered for processing the volume of messages that may be required while also playing the instrument - which you would want to do while editing and there are inherent delays . All this is pretty instant when you are using the front panel controls directly and it’s that experience I want to reproduce on the remote controller. Also, using the onboard sequencer is a non-starter due to the constance screen refreshes required.

When I’ve searched online, the closest I have found of people wanting to something similar is with the goal of capturing the actual text and/or values displayed on the LCD where for me I only want to be able to to retransmit the raw display signals, like-for-like to a remote display of the exact same type. That way I leaving all the processing on the Kurzweil without SysEx clogging the process.

So my question is how feasible is this?