GPIO access in C++

[bloodline]

Hi all,

I have written a simple GPIO class to allow easy access of the 17 GPIO pins exposed on the Raspi. So far, setting a pin high or low works and I also have software PWM working on any pin too.

A couple of issues I want to sort out before I throw this online for those that might find it useful.

I can't figure out how to read a GPIO pin yet, any clues please. I'm hitting the hardware not using the Kernel interface.

And my PWM is based on the nanosleep timer... unfortunately this is only stable to about 10us, so it fine for speed control and LED brightness... but does make servos a bit twitchy... do we have any realtime timers Linux?

[joan]

To read gpios.

Code: Select all

...
/* uint32_t  *gpioReg points to base address of gpio registers */
...
#define GPLEV0    13
#define GPLEV1    14
...
int gpioRead(unsigned gpio)
{
   if ((*(gpioReg + GPLEV0 + (gpio>>5)) & (1<<(gpio&0x1F))) != 0) return 1;
   else return 0;
}
...

You'll need to use the DMA hardware to time your pulses if you want accuracy.

[bloodline]

Cheers!