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

[Philip Covington]

On 5/11/06, Lyle Johnson <kk7p at wavecable.com> wrote:
> 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

Phil, Lyle,

OK, I am looking at the PCA9534 for the I2C port expander.  It is 5
volt tolerant.  This should take care of our 8 bits of input I hope?
I can also connect the interrupt line to the FX2.

For 8 bits of output I can use another PCA9534 coupled with a ULN2003A.

How does this sound?

--ALSO--

Phil H sent me another link to a ESD protection device by Littlefuse
(SP0503BAHT).  That got me to looking at their app notes and they have
a device (PGB002ST23WR) that is recommended for USB 2.0 (<1 pf
capacitance) that comes in a nice SOT23 package.  One device will take
care of the USB port.  Digikey and Mouser both carry them.  I plan to
use it.

LYLE:

I cannot seem to find a datasheet for the TPIC595D device.  Is the
part number correct?

73 de Phil N8VB

 1147447078.0