The Pro-2011 and PROgramit are an ideal match, the scanner is easily connected to the PROgrammit hardware and the software solves the problem of having only 20 channels.
The connection is pretty stright forward, there are no special requirements or tricks and you don't even need a 100x magnifier to see what your doing, everything is well spaced out and solder points large and accessable.
Remove the bottom of the scanner by undoing the six screws, the plate will lift away to reveal two pcb's, one large pcb with the antenna socket soldered onto it and one smaller pcb, it is the smaller pcb that contains the keyboard circuitry we need.
This smaller pcb not only contains the keypad circuitry, it also holds the CPU chip and some of its support componentry, RS call this the "LOGIC" pcb. The larger PCB contains the RF, AUDIO and POWER sections, RS call this the LINEAR PCB.
The larger pcb covers some of the solder points we need, so remove the four screws that hold it in place and unsolder the very short wire that goes from LOGIC GND on the large pcb to the big solder blob on the logic pcb, you should now be able to lift the board off to one side and fully expose the logic pcb. Now would be a good time to have a look at the image file supplied in this archive.
At the top of the pcb you will now be able to see five diodes, labelled D203 to D207, these give access to the columns, and down at the bottom of the pcb will be four resistors, labelled R202 to R205, which give access to the rows.
Using the image file you can see where we solder our take off points from. For the diodes it is the cathode side, with the resistors it is the "live" or cpu side (the other side of the resistors is connected to ground ). The labels, X0 to X4 and Y0 to Y3 correspond to the those in the PROgramit schematic.
For those experimenters out there I have located the "SCAN CONTROL"
signal, labelled as NOTE 1 on the image file. This line is LOW if the squelch
remains unbroken (no signal) and goes HIGH when a signal breaks the squelch.
It will remain in this state for the duration of the transmission.
Anyway, back to the project...
I built the PROgramit interface exactly as described, including the diodes on the X inputs and the resistors on the Y inputs.
Don't forget to resolder the LOGIC GND wire when you put the LINEAR PCB back in place!
At this stage the rest of it is up to you. You could mount the whole thing inside the scanner taking care to find somewhere where it wont short out against any other components or the mains power. The +5v supply can be obtained from within the scanner so all you'd have to do is mount some sort of data connector somewhere like a DB15 or DB25. There's not alot of spare room inside the scanner so good luck if you take this route.
I put a DB25 female on the side of the scanner and ran the wires from
the diodes and resistors on the logic pcb direct to it. The PROgramit hardware
was mounted in an external box that had a DB15 male on one side and a DB25
male on the other.
The advantage of this setup is that the interface doesn't have to be crammed into a tight space and it can also be used for multiple scanners, saving the hassle of building the same thing for every scanner you own. This setup also works great for hand held scanners where you have no free space to install an extra circuit board, as long as you still have enough room to fit some sort of external multipin connector. I found the high density 15pin VGA connectors ideal.
So far I have used modified my Tandy/RS PRO-2011 and AOR AR-1000XLT to work with PROgramit, so the "multi scanner" idea works! (AR 1000 details are available seperately) And with almost no spare space inside the AR1000 there would have been no choice, infact there was barely any space for the high density DB15 female. I *ALWAYS* put a female connector on the scanner so the scanners circuitry isnt exposed to the outside world, protecting against possible shorts or static discharge.
The only disadvantage to this idea is you will need an external power supply, see the serial interface schematic for simple supply circuit using the LM7805 ic. I put a DC power connector on the box and use a 12v plugpack.
As well as this document and the image file, in this archive you'll
find the PRO2011.DAT file which sets the PROgramit software parameters
up to suit the scanner.