GXP Gadgeteer Bridge

Is the GXP Gadgeteer Bridge just a way to add 4 Gadgeteer ports to say a FEZ Cobra III or is it specialized to connect a display?

I am thinking of using it to connect a RS21 WiFi module to the Cobra III.

Anyone already doing that?


Yes it can be used to connect a networking module. That is what the SPI socket for.

@ Greg Terrell -
Greg, I have done what you are talking about doing and it’s working. I connected the RS21 module to the SU socket on the GXP, and then connected to a time server (so I can accurately set the real time clock when powering up).

The socket you want to use is the SU socket on the GXP bridge (so far as I know there is no SPI socket on the GXP bridge). You need to do a little signal tracing determine the correct pin parameters for the WiFiRS9110 object constructor. These refer to the signals present on the GXP bridge you need board to construct the WiFiRS9110 object. The SPI bus that goes to the SU socket on the GXP bridge on a Cobra III is the FEZCobraIII.SpiBus.Spi2. I guess you can safely ignore all the warnings about using Spi2 with networked stuff because of its internal use on the Cobra III. I guess the Cobra III correctly handles the chip select line to prevent conflicts.

The chip select, interrupt line, and the reset line need pin research. Here is what works on the Cobra III (It’ll probably be different on other main boards with a GXP socket):

var wifi = new WiFiRS9110(  
   FEZCobraIII.SpiBus.Spi2,  // SPI module 
   FEZCobraIII.Gpio.D51,     // chip select
   FEZCobraIII.Gpio.D50,     // external interrupt
   FEZCobraIII.Gpio.D59);    // reset

By the way, I’m sure you know you need to add a copy of the static class FEZCobraIII in the GPI.Pins namespace into your project so you’ll be able to reference the following pins:

o FEZCobraIII.SpiBus.Spi2
o FEZCobraIII.Gpio.D51
o FEZCobraIII.Gpio.D50
o FEZCobraIII.Gpio.D59

The location of the file with that static class is in the resources (I think) for the Cobra III board.

Just so you know, the SU label means it’s both an S socket and a U socket. That means it’ exposes the necessary SPI pins as per the Gadgeteeer design, as well as the UART pins as per the Gadgeteer design. So your statement about the “no SPI socket” isn’t correct, it clearly is an SPI socket but also is more than that…

@ Brett -
Thank you. I stand corrected. What I should have said: “The GXP bridge board has no socket [em]labeled[/em] SPI”.

I don’t use Gadgeteer sockets (except those Gadgeteer sockets that appear on my GXP bridge board). I generally pay little attention to the signal line capabilities of Gadgeteer sockets that my Cobra III board gained from attaching the GXP bridge board, referring to them only by their silk-screened identifiers on the GXP bridge board.

I thought that Greg, a newbie, might benefit from having a direct reference to the specific GXP socket to use for the RS21 module, rather than an indirect signal name or signal capability reference to it.

Thank you all for the responses… they helped considerably. I was able to review the schematics again and with the input received was able to better understand the GHI ecosystem.

Ordering my parts today! ;D


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absolutely correct, although typically I’d expect most people including new people will try Gadgeteer which would mean you shouldn’t need pin definitions, but I do appreciate your work on the pinouts for those who need it