Si5351 breakout board and Tiva C

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mattn2
 
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Si5351 breakout board and Tiva C

Post by mattn2 »

Hi,

I'm using the SI5351 breakout board with a Tiva C launchpad ARM board - but I'm having problems with I2C. When I do a read, all I ever get back is 0x00. I'm checking the I2C error function and that reports no errors (swapping leads around or changing the address always causes an error and 0xff to be read). If I connect up my arduino to the si5351 board everything works as expected. I'm using the same I2C code on the Tiva C to talk to a bmp180 and tsl2531 breakout boards and they both work fine - so I'me somewhat confused!

Any suggestions as to what to try next?

Thanks,

Matt

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adafruit_support_mike
 
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Re: Si5351 breakout board and Tiva C

Post by adafruit_support_mike »

Try adding pull-up resistors to the SDA and SCL lines.

The SI5351 breakout has a built-in level shifter that allows it to work with input values from 3v to 5v. The pull-up resistors that are visible to the chip aren't visible to anything off the PCB.

mattn2
 
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Re: Si5351 breakout board and Tiva C

Post by mattn2 »

Unfortunately that made no difference. Looking at the circuit diagram, there are 10k pull up resistors on the Vin side of the BSS138.

Thanks,

Matt

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adafruit_support_mike
 
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Re: Si5351 breakout board and Tiva C

Post by adafruit_support_mike »

Hmm.. post a photo of your hardware and connections and we'll see if those give us any clues.

mattn2
 
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Re: Si5351 breakout board and Tiva C

Post by mattn2 »

Unfortunately I've been busy/away with work. When I got back to it yesterday afternoon, the micro-USB connector detached itself from the Tiva C PCB. I'll try with one of my other 3.3v ARM boards - but that may take a bit longer as I'm a but rusty on them....

Thanks,

Matt

mattn2
 
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Re: Si5351 breakout board and Tiva C

Post by mattn2 »

So I ended up buying a new ST Nucleo F103 ARM board (the USB falling off my Tiva-C was the last straw for it - its not the first Tiva-C I've had fail on me that way). I connected the Si5351 board up and its fails in exactly the same way - whenever I2C reads anything from it, its always a zero. On the same I2C bus I also have a Sparkfun BMP180 connected which works fine. I have tried with the si5351 on its own, same zero only response. I've also added 4.7k pull up resistors, same zero only response. If I disconnect the SDA line then the code falls over with an I2C error. So it appears to me that everything is working apart from the fact that the si5351 only wants to send zeros.

Can anyone confirm it does work with a 3.3V system?

If I get time next weekend, I'll attach my 'scope & logic analyser and see if that tell me anything.

Thanks,

Matt

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adafruit_support_mike
 
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Re: Si5351 breakout board and Tiva C

Post by adafruit_support_mike »

Just hooked mine up to a 3v Pro Trinket and was able to program it normally.

mattn2
 
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Re: Si5351 breakout board and Tiva C

Post by mattn2 »

Thanks for checking for me.

With the help from my logic analyser, I managed to track down what turned out to be a stupid bug in my I2C read function.

So everything works as it should now.

Thanks again for all your help,

Matt

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adafruit_support_mike
 
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Re: Si5351 breakout board and Tiva C

Post by adafruit_support_mike »

Glad to hear you got it working. Happy hacking!

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