The Mux
Because this is primarily a video device, its inputs and outputs are described in the Vision Path section.
The device on the desk controls main mux. Press one of the four blue buttons, and then on of the 32 grey buttons according to which of the 32 inputs you wish to go to one of the four outputs.
I've forgotten what the red buttons did, but they're now redundant.
The main mux is the huge black thing in the AV rack, it routes video to different places, and also has analogue TV demodulators in. The main mux is controlled by an outboard box which sits on the directors/vision mixers desk.
Functions
- 32 input to 4 output matrix
- 2 Nicam stereo tuners
Faults
2 composite inputs to the matrix are dead.
controller
pinouts
| 1 | +5V power |
|---|---|
| 2 | 0V ground |
| 3 | 32x4 crosspoint switch control lines |
| 4 | consisting of a clock (rising edge trigger) |
| 5 | CS (active-low) and Data |
| 6 | NC |
| 7 | Station Tuner control (I2C Data) |
| 8 | Net Tuner control (I2C Data) |
| 9 | Station/Net Tuner common control line (I2C Clock) |
explanation of operation
This was originally based around a PIC16F84 with an 8MHz crystal containing code written by Rob Sprowson. The hex file as loaded into the PIC can be found here[[1]] whilst a partial disassembly of it can be found here [[2]]. Also available is a disassembled version of the ROM code [[3]] from within the BBC micro that used to be part of Schedula.
A new PIC, a PIC18F2455 using a 20MHz crystal, has replaced this PIC through use of an extra 'daughter' board. This change in PIC was to allow easier coding, using C instead of assembler, and to provide USB capabilites. The source code can be found in Main Mux Source Code.