Any idea of how i can use ethernet shield and another SPI device? I'm think in a mux but the ethernet shield will always connect to arduino :S

I'm using that library http://code.google.com/p/jeelabs/source/browse/trunk#trunk/libraries/RF12%3Fstat...

The device is a RFM12

I would change /SS to another pin in RF12.cpp and see if you can get that to work by itself and then add in the Ethernet Shield later.

The datasheet for the WIZ811MJ (used on Adafruit's current Ethernet shield) says it has an inverter on-board that properly drives SPI_EN from SS.

It also says one of the differences from the older WIZ810MJ is that the old module requires control of SPI_EN.

So maybe it depends on which version of the Ethernet shield you have?  Were there boards shipped that used the WIZ810MJ module?

I've got some SPI LED driver chips,  and I've been meaning to put together a numeric display with one.  I have another project due tomorrow,  but I can try to get the display to co-exist with the WIZ811MJ later.

Have you looked closely at the standard Ethernet libraries to see whether they have any features like using interrupts (as the RFM12 apparently does),  or depending on the previous state of the SPI registers,  that might make for ugly surprises?

Ran

Quote:

I was referring to the official ethernet shield, as described here.  Hopefully other shields work around this issue.

If you've got a standard Arduino ethernet shield, the RFM12 library will not work with it because a) the ethernet shield won't go hi-Z on MISO, and b) they're both hard coded to use 10 as the SS.  You can hack the software to get around the latter, but I don't know how to get around the MISO problem without either completely rewriting the RFM12 library to bit-bang SPI on pins other than 10-13 or doing some serious hacking on the ethernet shield.

Other ethernet shields that are software compatible with the official shield may or may not have the hi-Z MISO problem, but they'll still be wired to use 10 as SS, which will require changing the RFM12 library to use a different pin for SS.

-j

And if in last option i use an mux to mux the 10 11 12 13 to the two devices?

       / RFM12
10  --
       \ Ethernet

       / RFM12
11  --
       \ Ethernet

       / RFM12
12  --
       \ Ethernet

       / RFM12
13  --
       \ Ethernet

Quote:


Then you wind up with a problem.

However,  there is an "else" available  

You need to actively drive the SS line on both devices all the time.  So,  no muxing there.

And you can drive both SCLK and MOSI,  so no mux needed there,  either.

I checked the Ethernet schematic,  and there's a 2-pin jumper that allows SEN to be connected to ground.  It should be possible to connect that to a different digital pin,  and use that to drive SEN.

Since SEN is active-high,  and SS is active-low,  it might be possible to connect the RFM12's SS to the Ethernet's SEN.  Well,  of course it's possible,  but I'm not sure it will work.    There could be a timing problem:  since SEN is doing some bus reconfiguration,  there might be a time lag before it takes effect that could still cause interference.  Or there might not.

Either way,  it's worth a try.  If it doesn't work out,  just assign a different pin to the RFM12's SS,  and add delay(s) around the toggling of SEN as needed to make it work.

It's definitely easier than trying to build a mux.

Ran

You need a second try  

The SS signal is "active low",  and SEN is "active high",   so you need to flip the 1s and 0s in steps 3 and 4.

Set the Ethernet's SS to 0,  and SEN to 1,  to talk to the Ethernet.  Set them opposite to talk to the RFM12.

Someone mentioned that the RFM12 driver is using interrupts.  You'll need to modify that.  You might be able to just disable that interrupt while talking to the Ethernet.  Or you might need to make more complicated changes.

Ran