Re: [Discuss-gnuradio] 16 digital I/O lines to control external devices like antenna switches

[Harley Myler]

I traced those from the WBX simple GDB, through the WBX and to the USRP2. They 
wind-up at U1 (XC3SXX00FG456−IO7(tx)) and U1 (XC3SXX00FG456−IO2(rx)) on page 3 
of 8 of the USRP2 schematic. I do not know why they are both labelled "U1". The 
date, revision and drawn-by blocks only had tokens. I may be looking at a 
preliminary schematic.

So at this juncture my assumption is that the FPGA(s) given by the XC... labels 
above, although I cannot find a Xylinx part number match, simply run out to the 
20 pin header connector on the daughterboard. Of the sixteen lines, each 
daughterboard usurps--an ironic term here--any number of the available 16 GPIOs 
for their own purposes and what is left are available to the user.

As such, my conclusion is that the following, per the schematic, are available:

RX Control Pins io_rx[15:14] −− Unused
TX Control Pins iotx[15:8] −− Unused

This gives 9 GPIO pins available to the user, hardly 16. The product 
documentation should reflect this. Nevertheless, nine will be adequate for my 
purposes.


On May 21, 2010, at 12:46 AM, Matt Ettus wrote:

> On 05/20/2010 10:45 PM, Marcus D. Leech wrote:
>> On 05/21/2010 01:37 AM, Matt Ettus wrote:
>>> 
>>> 
>>> Each daughterboard connector has 16 GPIOs.  Some of them are used by
>>> the daughterboards, but others are available for your use.  On the
>>> WBX, io_tx[14:8] are available for you to use, and they come to the
>>> connector on the grand-daughterboard.
>>> 
>>> If you need to synchronize the action of these pins precisely, the
>>> bets way to do this is by modifying the FPGA.  If you just need to
>>> turn them on and off from software, you can do that with the API.
>>> 
>>> Matt
>>> 
>>> 
>> The schematic for WBX makes it look like a couple of the io_rx are
>> available as well--are they not?
>> 
>> 
> 
> 
> Yes, some others are available as well.  You need to look at both the wbx and 
> grandaughterboard schematics.
> 
> Matt





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