[hpsdr] [JANUS] Offloading SDR-1000 reguired I/O from OZY

[Lyle Johnson]

Hello Phils!

> If there is room on the OZY, what if I add a port expander (I2C or SPI
> or ?) to the board and provide 8 buffered ins and 8 open collector
> outs?  That way I can avoid using up all the extra  I/O but still
> provide some protected IO on the OZY for purposes where a separate IO
> board is overkill?  I will look at that tomorrow...

TPIC595D from TI is a SPI compatible, 8 bit, open collector output, 
reasonable current sinking, separate latch so as you shift data through 
it nothing changes until you want it to, can be cascaded, reset to start 
with all outputs open, small and dirt cheap.

PCF8574 (8 bits) and PCF8575 (16 bits) are I/O parts for I2C, also from 
TI, also cheap.  If operating from 3.3V you can't drive them with a 5V 
signal; limit is Vcc+0.5V.

Maxim has some nice parts in their MAX73xx series, but, since they are 
*interesting* Maxim parts, you can't really buy them :-/

73,

Lyle KK7P


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