[ts-7000] Reading GPIO ports

[Matt Godbolt <>]

Hi all,

I'm quite likely making a very schoolboy error here, but I'm currently investigating getting an IR detector plugged into my ts-7250.  I have my external IR circuit all set up and (possibly) working...but I'm having difficulty in reading the output from my detector.  Upon further investigation I discovered I can only intermittantly read port B.

My test setup is the button.c example code modified to printf("hello!\n"); instead of flash the LEDs, a wait for the logic level to return to 1, and with a for(;;) around the outside so I can continually monitor for bit 0 port B going low.  For input I've used a ribbon cable plugged onto the DIO port and I'm literally just holding pin 1 and pin 2 together manually.  The code runs, and correctly detects my wire tapping skills, but the reads seem to take ages to notice my change.

In fact, unless I hold the wires together for more than about a half second, bit 0 doesn't go low at all.  I've tried everything I can think of from the software point of view, but I'm now stumped.  I've disabled the debounce that the button.c sets up (though from reading the Cirrus docs this only affects the interrupt capabilities).  I've tried setting up interrupts and I've tried using the RAWINTSTSB port instead - all seem to suffer the same delayed fate.

>From the point of view of reading the demodulated output from the IR detector I need to be able to make fairly fast readings of bit 0 to determine the pulse/gap ratios to find the actual bit stream of the remote controls I'm using...

So my question really is; am I doing anything stupid here?  I'd have thought the GPIO inputs would be instantaneous.  I'm more of a software guy than a hardware guy, and so the only thing I can think of is that maybe if the GPIO memory is cached then I could be reading old data from the processor cache instead of the actual port...but then I'd imagine all the other peripherals would have the same problem (and the LCD sample works just fine).

Any thoughts or hints gratefully received, I'm rather stumped at the moment!

Thanks in advance,

Matt
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