Well, sort of
More a "which way should I jump" challenge.
Smallish run commercial project - say 100 to 200 units.
Cheaper would be nicer but labour costs will predominate.
Lower than higher current nice.

Processor sends serial to a printer, serial from a GPS, serial from a card
reader, reads/writes a 32K IIC eerom, talks to a central processor.
All inter peripheral links are N81 ASCII at true RS232 levels. All data
links are at 4800 baud.

Want to get this going with minimal effort and cost. At present Scenx with
virtual peripherals seems the probable easiest.

3 x 4800 UART receives
2 x UART TXs
1 x EEROM read/write
GPS data filtering
Data request/write control
Data direction to/from peripherals.

Send data to central processor via 4800 baud link.
Abort GPS read if card reader starts.
Can handle card reader and eerom write if both overlap.
Maybe queue card reader if occurs during eerom read but maybe abort block
read and repeat thereafter.
eerom read / write is always either 2 bytes or 64 bytes.

GPS should have output filtered to normally only forward RMC string (coz at
4800 baud this takes about 15% of channel bandwidth with 1 second update
whereas all standard messages take about 85%).

With virtual UARTS with say 4 samples per bit at 4800 baud that's 50 uS
polling cycle.
Scenix handles with ease.
20M PIC also really.
Just maybe a 4 M PIC (maybe).

Anything out there with 3 hardware UARTS and costs about nothing ?(I'm being
lazy)

Could just about do this with 8 i/o lines (2 x TX, 3 x RX, 2 x IIC = 7)
Something else will crop up needing at least one more.

Modest EEROM on chip would be nice but not essential.

Scenix is not cheap and is power thirsty but the virtual peripherals do look
attractive.

Any thoughts???


      Russell McMahon
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