On the other hand if I change the i2c-test program on the robostix to drive
the pin high by default (initially), before it accepts any input., then I
notice that the pin only gets driven to 2.5 V.
Maybe the gumstix pins are in some state that cause the voltage to drop.
Since I don't do anything to the gumstix side of things. This is without
running the gumstix i2c-test program.
> hi Dave
> My think worked for a while and then stopped. I could cycle through the
> various states of the SCL pin on the robostix using the i2c-test program
> on the gumstix. and get the right results. I tried using i2c-load during
> this time but got the same error that it could not locate 0x0b. Now I am
> back to square one. Things have stopped working.
> However, I noticed something interesting. When I run the i2c-test program
> on the gumstix, my SCL pin does get pulled high. Or for that matter even
> before starting the program. Essentially the robostix i2c-test program in
> running on the controller and the first thing it does is to set the
> robostix SCL, SDA ports as inputs. And then the robostix i2c-test program
> waits in a while loop, waiting for a character input from the gumstix
> i2c-test program. And in this state the SCL,SDA should and they do get
> pulled high to 5V.
> The problem is when I run the program and start changing things. The
> robostix i2c-test program essentially changes the states of the robostix
> pins. It changes between driving high, low and changing to input. When I
> cycle through these states and again make the SCL pin as input, then it
> stops being pulled up. In fact even when I change the state to high, the
> SCL pin goes to 2.5V instead of 5V. Is it something the gumstix side of
> i2c-test program does that changes things?
> And yes, if I remove the gumstix and then change the state of the SCL pin
> to either low, high or input, I get the right results ie 0, 5 and 5 (since
> it is being pulled up) resp.
> Everything on the NXP chip is fine, when I ground the 3.3 V side I get a
> 0.5 V on the 5V side, which I think is fine. This is when I have
> configured the SCL pin on the Robostix as an input.
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