[sdiy] Module format

[Neil Johnson]

Hi Paul,

Paul Maddox wrote:
>> I did a quick sanity check on the choice of connector, the so-called 
>> industry-standard 30-pin SIMM socket.
>
> good idea.
>
>> Farnell - don't stock
>> Digikey - don't stock
>> Rapid   - don't stock
>> Maplin  - don't stock
>> Mouser  - don't stock
>> RS      - some lines stocked, but reducing, and only sell to trade 
>> accounts
>
> I'm getting old...

Know the feeling.

>> Me, I'm looking at half-size DIN41612 connectors for the 
>> re-engineering the mini modules.  They have plenty of pins (I'm going 
>> for 32), gold-plated if you feel the need, good mechanical support 
>> for boards, and so widely available I expect to see them still in 
>> production while enjoying a meal at Milliways.
>
> sounds like a plan, I guess you buy the 'right angled' ones for the 
> modules and the 'straight' ones for the motherboard, yes?

Correct.  The right-angle plug goes on the module, and the vertical 
socket mounts on the backplane or motherboard so the modules stand 
upright.

Quick look in Rapid catalogue suggests:
19-0160	32-way plug		63p
19-0162	32-way socket		78p

The scheme I'm looking at for pinouts is to have one row all GND, 
leaving 16 pins for power and I/O.  Power is +15V/-15V, leaving 14 pins 
for everything else (which should be sufficient).  That way, if I 
decide I want to mount a module in a box rather than use a backplane, I 
can put a 0.1in header strip and hand-wire twisted-pair or shielded 
cable, which each signal having a corresponding GND.

If any module needs +5v this can be generated locally with a linear 
regulator, which has the added benefit of localising any +5V rail noise 
(as only 5V logic would need a 5V rail).  And I need to do any logic, 
I'm more likely to slap on a CPLD or FPGA and run it off 3V3 from a 
small switching regulator.

Cheers,
Neil

--
Neil Johnson <http://www.njohnson.co.uk>