I'm encountering some strange pin behavior.

Brief background:
  • I'm using I2S pin functions, which requires me to use pin 13 (PTC5) as ALT4 (I2S0_RXD0).
  • I'm also using SPI, so I need to use pin 14 (PTD1) as ALT2 (SPI0_SCK).
  • Using pin 27 (PTC9) as ALT4 (I2S0_RX_BCLK).
  • Using pin 28 (PTC8) as ALT4 (I2S0_MCLK).
  • Using pin 29 (PTC10) as ALT4 (I2S0_RX_FS).


For reference, I'm setting the alternate pin functions using this code.

I was using pin 10 (PTC4) as a general purpose digital input to monitor the Power Good line from a regulator, however after a fair amount of troubleshooting I discovered that something about my setup was causing strange values on that particular pin. When the regulator pulled that line high, it was only going up to 1.65V instead of 3.3V. I unhooked the line and measured the pin on its own, setting it to high and low. If I remember correctly, the values were roughly 0.7V for low and 1.65V for high! I moved the Power Good line to pin 3 (PTA12) and it works fine.

So now I'm hesitant to use pin 10 for anything, and I want to know why. Could changing the function of pin 13 (PTC5) be affecting the function of pin 10 (PTC4), or is it something else altogether? I'm happy to run additional tests to help isolate the problem, if need be.

Thanks, -Dan

PS. On a tangential note, I'm wondering if there's a neat part that can be used to elegantly breakout the 14 pins on the bottom of the board? Right now I'm just soldering wires to them, which works, but can be annoying when anything needs to be modified. Specifically I'm wondering about a good solution for breadboarding, and also a good solution (perhaps different) for interfacing these pins with a PCB. There's a nice white box printed around them, so what exactly is designed to go there?