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Software Application Development Getting I2C up and running
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Related

Getting I2C up and running

troy.cowan.123
troy.cowan.123 over 8 years ago

Hi. 

I'm trying to get the I2C functionality going in my application (running on a picozed).

As far as I can tell I've set up the PL correctly, enabling I2C 0 and connecting it to pins 50 and 51. In the PS, I'm using the iicps_v3_3 driver built into libxil.a. I'm calling the methods pretty much exactly as is done in the supplied example. When I attempt to send a couple of bytes out on the bus, nothing happens. I'm scoping the SCL and SDA lines, and they are not changing state at all. I never see the COMP bit or any error bit become active in the I2C registers. It's as though the I2C functionality is just inert or disabled. I'm stumped as far as how to troubleshoot this issue. Any help would be great, thanks!

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  • zedhed
    0 zedhed over 8 years ago

    Hi Troy,

    I2C protocol requires an external pull-up resistor on each of SDA and SCL lines to allow the transitions from 0 logic state to 1 logic state.  What type of pull-up resistor values are you using on pins 50 and 51 on your PicoZed Carrier card design?

    Best Regards,

    -Kevin

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago

    4.7K ohms

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  • jafoste4
    0 jafoste4 over 8 years ago

    Hello Troy,

    Have you taken a look at Tutorial 09 PL I2C PMOD located here? http://picozed.org/support/design/13076/106

    --Josh

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago
    .
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  • jafoste4
    0 jafoste4 over 8 years ago

    Hello Troy,

    It seems like your trying to set up the PS I2C Controller on your PicoZed. If you refer to the PicoZed FMC Carrier Card V2 Hardware user guide located here http://zedboard.org/support/documentation/13076 you will notice in section 2.7 there is a note stating the PS_PMOD interface on the PicoZed SOM is by default is set to eMMC mode and not to the PS_PMOD your trying to interface to.

    In this case you can either use the resistor jumpers on your PicoZed SOM to have the default be to the PS_PMOD or you can toggle the MUX via GPIO in your application code. For an example of toggeling the MUX via GPIO please download the Tutorial 08 PS I2C PMOD reference design located here http://zedboard.org/support/design/13076/106

    In that reference desing please refer to the following directory \Supporting Documents\I2C\PS_PMOD\PicoZed. Look through that example code and you will see how I enabled the GPIO library and toggled the MUX's GPIO.

    --Josh

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago

    Hi JFoster, thanks for your reply.

    We're not using the carrier board; it's our own design. And we're not using any PMOD. We're also not using an I2C IP block in the PL; we've just set up MIO pins 50 and 51 as I2C pins in the PL and are using the integrated I2C in the PS.

    Man, that's a lot of acronyms. Hope I got that right.

    Troy

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  • zedhed
    0 zedhed over 8 years ago

    Hi Troy,

    Just making sure that I understand this correctly, you have configured your Vivado hardware platform to route one if the PS I2C controllers to MIO pins 50 and 51 and so you are not using the PL for any portion of the I2C interface, correct?

    Can you describe what you see on the SDA and SCL lines?  You mentioned that there is no toggling, are the lines stuck logic high or low?

    Best Regards,

    -Kevin

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago

    Yes, you described my setup correctly. The lines are both stuck logic low.

    Thanks,

    Troy

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago in reply to troy.cowan.123

    Whoops, sorry: one line is held low (SCL), and the other is high (SDA).

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  • troy.cowan.123
    0 troy.cowan.123 over 8 years ago

    Turns out I had some code hidden away that was re-purposing pin 50 out from under me. All set now.

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