This page will report the progress of the Matey Modem prototype page. Updated each week.
Updated March 2005 with some colour pics - showing their transmission times.
Some Initial Tests of Colour Capture
Compression for colour images is now working. These large, bitmap images were captured by the Matey prototype and transmitted with three levels of compression.
The horizontal colour tear lines are the synch separator not set up correctly. Also, the jaggedy verticals are also due to this. Needs a minor fix. The colour strips down the edges are dedbugging info, to be deleted once I have the final colour balance working.
Hot Issues Under Development
The schematics are in this file PDF. Note that the varactor diodes around the video capture crystal are no longer needed.
The OLD scans of the schematics are in this directory. They are for the monochrome version.
A third relay has been added in case there should be any break-before-make problem with the exchange. Also, a pair of links are added to solve the same problem on the instrument side, but note that this will cause temporary direct connection of the local PSU to the line. This is ok if the local supply is floating, as in normal operation, but can be a consideration when scopes or laptops are connected to the unit, since these can upset grounding.
Trials over a number of different phonelines are envisaged for the next few weeks.
Sub-Assembley Status - Components Requiring Work Listed Only
The announced message is being implemented. DOWNLOAD AUDIO SAMPLE.
I have written a program to take a wav track, downsample and compress it and download it to the flash.
This is software yet to be written.
The PAL Colour capture is being prototyped at the moment. For economy the horizontal dot clock will be 4.33 Msps so the max horiz resolution will be 216 pixels.
Remote Dial in Modem CodeThis has been planned. It will be V.22 1200 baud to start with. A standard V.8 connect sequence will be used so that a standard modem can be used to dial up the remote mateys.
Receive Modem / Laptop Environment
Some basic receive code has been written but a lot more work is needed. The laptop sound card has not yet been physically connected to the phone network.
It is intended to use a stero capture card on the laptop (they are all stereo) and use one channel for the local signal and the other for the line signal. This enables the CO hybrid to be implemented in software on the linux as an offline processing stage. The canned message can also be played out of the laptop from a wav file if desired.
Case, PSU and Environment
No work yet.
Working - needs to be extended for colour. Needs speeding up too. Not hard.
Craft PortThe CPU craft port is 4 pins at TTL level (power, ground, din, dout) for RS232 at 19200 baud.
The initial spec is here LASHUP SPEC 1.
Bill of Materials - BOM. Resistors and capacitors not listed.
Note that no attempt has been made to consider temperature range outside 0-70 in the listed part numbers.
All quantities are one off unless otherwise stated. The parts labeled AMG are available from the Audio Marketing Group in Haslemere.
Remaining components are mounted on the PCB 100x16 Eurocard.
For the processor core:
For video capture:
For the optional extras:
For the power supply:
For the POTS Hybrid Sub Assembly:
Certain of the BC817 may be instead: 2N7002 VSIL SOT23 (17) N 0.11 7.50 0.20600 5 (RS 237-0907)
The BB audio DAC is not longer used, all three DACs are now on the FPGA.
Additional Information Required
Availability of FPGA.
Note that in the UK a 'master box' is needed before the phone will ring. The matey prototype discards any master box functionality on the exchange side and hence a master box must be installed between matey and the instrument for the instrument to ring.