Using I2C with FullSpeed USB

[mister_e]

Sure it have 8 bits... 2 successive read .. well something like stated somewhere in the MCP datasheet. It must exist a quick drwaing of it somewhere in.

if you really want to add stuff, 4 choice spring to mind

use a bigger PIC than the 16F28, then just read the i/o, send it to the 4550 via USART.

Use a keypad decoder like 74c922

Use a single (or more) A/D pin of the 4550 with a multi-step voltage divider... yisssh

Find a multiplexer... time is short now, but it have to exist, i had the 4067 idea... but i'm not sure... i must forget something on this chip.. what? i don't know.

[Demon]

I like the 74C922 keypad decoder, looks simple enough.

Robert


EDIT: Hmmm, looked simple enough until I saw the prices at DigiKey and Mouser. It's 1/2 the price to go with a MCP23016 and PIC 16F628.

[Demon]

Steve, the 4067 multiplexer/demultiplexer is even better and only $2.08CAD at DigiKey.

The only problem is that I don't understand how to get it to go 'backwards'. The A0-3 pins are always referred to as inputs, I need them as outputs. I'm sure there's a way 'cause these are called both names, they must process both ways, no?

Robert


EDIT: "The CD74HC4067 and CD74HCT4067 devices are digitally
controlled analog switches that utilize silicon-gate CMOS
technology to achieve operating speeds similar to LSTTL,
with the low power consumption of standard CMOS
integrated circuits.
These analog multiplexers/demultiplexers control analog
voltages that may vary across the voltage supply range.
They are bidirectional switches thus allowing any analog
input to be used as an output and vice-versa. The switches
have low “on” resistance and low “off” leakages. In addition,
these devices have an enable control which when high will
disable all switches to their “off” state."

It should work.

[Demon]

74HC148 encoder here:
http://www.st.com/stonline/books/pdf/docs/1903.pdf

Page 7 has a schematic to cascade 2 chips with 16 inputs to 4 outputs. $0.31CAD when I buy 100 at DigiKey and I only need an AND and NOT gates to go along with them.

Robert