Remote control of audio equipment over RS-232 with Arduino

These questions are following on from my previous question Reverse engineering old serial devices and cloning with Arduino about the monitoring of RS-232 traffic.

I had some good success and now have some questions about the general approach to take.

Over the past week I have been mapping out the controls of a rather ancient RS-232 remote control for a piece of audio equipment. Using port monitoring software etc., I now know what each control sends in terms of messages etc.

The device has 6 faders, 24 buttons, and can display 48 ASCII characters split into 1 lcd of 2x12 chars and the other 1x24 chars.

The remote also has a stereo dB level indicator made up of 2 rows of 16 LEDs.

I want to re-create the device using Arduino and so far I have come up with this.

PROBLEM 1

The six faders are easy enough without even needing a multiplexer (I think, at least on the ProMini) these vales can be read in, mapped from 0 to 255 and the output of each would need to be converted to HEX and have the corresponding control byte prepended to it's value before being spat out on the serial bus.

PROBLEM 2

The 24 buttons I think will be somewhat more of a challenge, I'm wondering if there are keypad or scanning options I could try for this as there are not 24 inputs available.

PROBLEM 3

As I mentioned above, there are 2 screens in the device, a 2x12 at the top and a 1x24 at the bottom. I believe these screens are chained in some way because If i send more than 24 characters to the 1st display they will overspill onto the bottom (1x24) display.

The commands come over the RS-232 bus like this:
each message of text begins with <00> and ends in <03> so a full 24 character message would look as follows:

00 74 68 69 73 20 69 73 20 61 20 74 77 65 6e 74 79 66 6f 75 72 63 68 61 72 03


but if this message were longer, how would I want to think about spilling over onto the next screen?

I guess these are 3 large questions that maybe I should split up. I just wanted to get this all out in context.

• It's funny that the grammar police come and fix all your posts here after you type them. I guess it makes sense, I'll try to be more attentive. ;) thanks – Brad Holland Sep 18 '14 at 15:39
• They're more like the grammar janitors. They can't write you tickets or put you in jail. Just keeping the site clean. :) – JYelton Sep 18 '14 at 20:54
• On another note, I think your question and concept are good, but it's kind of broad and unfocused. Perhaps you would get an answer if you can narrow it down. – JYelton Sep 18 '14 at 20:55
• yes I agree. in fact I'm going to close this and ask specific questions about the separate pieces. – Brad Holland Sep 19 '14 at 0:22