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CC1101 SPI communication problem

Gin Rossouw
Prodigy 60 points
Other Parts Discussed in Thread: CC1101, CC1070, CC1100

Hello

I am currently doing an upgrade of a product from a CC1070, to a CC1101.

A colleague of mine has successfully integrated the CC1101 into his design, and we have done various successful tests with this product.
The reference design supplied by TI was used.

I have used this same design, barring a few layout/routing changes. (I used a star topology for powering the various VDD pins,whereas my colleague did not in his first revision)

I cannot seem to communicate with the CC1101 over SPI.

I have verified my timings, using my colleagues product.
I have verified my timings with respect to the Application note on SPI communications to the CC1101.

I am clocking the device at 100kHz, which should be more than slow enough.

I have made sure that I did not over-voltage the device at any point.

I am not getting ANYTHING coming out of the SO pin. I have even lifted the SPI pin on my microcontroller (PIC18F46K20), to make sure the PIC is not maybe tying the line low, for whatever reason.

When forcing a power-up reset, I do not see the transition from high, to low, as described in the datasheet (indicating that the crystal is running, and stable)

However, when scoping the crystal pins, I can see that it is indeed running.

I have verified that all my surrounding decoupling capacitors are the correct value.

I have re-tried using several IC's, incase it was a faulty/damaged part.

I have also seen on an online forum that another customer has had similar issues, but the problem was not officially resolved.

Do you have any suggestions as to where I may be going wrong?

Any feedback, comments, or suggestions would be greatly appreciated.

  • 0
    Expert 1560 points

    This is Chris Pinter with Pinter Electronics Consulting. I am an RF Engineer and will offer you some suggestions. If you need to get a hold of me directly please visit http://www.pinterec.ca/contacthtml.html

    You can try the following steps.  This might help identify the problem.

    Unpowered tests

    1.     Grab a RAW PCB and inspect the traces for the SPI.  Could they be shorted together, ground, or to some other trace?

    2.     Check to continuity of the traces on your test board.

    3.     Measure the DC resistance on the Evaluation board and compare to your board.

    Powered testes

    1.     Apply power to the device.  Use an oscilloscope and measure the voltage on VCC.  Compare to the EV kit if necessary.

    2.     Measure the voltage on all of the SPI lines.  Compare to the EV kit if necessary.

    3.     Measure the voltage on any decoupling lines, intermediate voltage lines, etc.

    4.     Measure the oscillators.  Check the frequency, peak to peak voltage and waveform shape.

    5.     What is the SPI connected to?  Are there multiply devices on the same SPI?  Remove each one and test the SPI.

    If you need more help we can offer to take a look at the device and save you some troubleshooting time and headache.

    Don't be shy is asking for any more help.  :)

     

     bye for now,  

    Chris Pinter

    http://www.pinterec.ca

  • 0
    Prodigy 10 points

    Hello Gin,

    Can you please let me know if your problem is resolved? We are trying something very similar and our issues are almost the same.

    We have 3 other behaviours...

    1. In this case the SO always follows the CSn signal.
    2. In this case the SO always follows the SCLK signal
    3. In this case the SO is something like SCLK superimposed on inverted CSn

     

  • 0 in reply to Ravi Kashi
    Prodigy 130 points

    Hello Gin, I also would like to know if you found a solution to your problem, because i'm having the exact same issue, I have a board that I used with a CC1100 and have no problems configuring and now I used a CC1101 and it presents the problems you describe.

    I hope you or someone can help me on this.

  • 0 in reply to Pablo Valdenegro
    Prodigy 60 points

    Hi guys

    Sorry for taking so long to post a reply

    Yes, we have managed to get it working

    I imported a Mentor Pads re-use module from a colleague's project, who had the IC working in his current project.

    The schematic and layout was based on the Chipcon reference design, and was assumed to be correct, as it was working in an existing project.

    It turned out that DCouple and DGuard nets were swopped around by accident.

    Curiously enough, several of my colleagues boards were working, where mine did not.

    However, I used a star topology for VCC, where he did not.

    Cutting the VCC track to the DCouple capacitor, and wiring the Dguard capacitor to VCC resolved the problem.