I have an application where 6 lines from sensors come into the Photon’s “D” pins. On the Arduino, you could access a register called “PIND” (IIRC) and that would read all 8 pins and return a byte. Does the Photon have an equivalent capability?
I quickly glanced at the link @ScruffR suggested in a past post – “Understanding the STM32F0’s GPIO part 1” – and it looks like the chip has this capability, but is it available to the software? And what’s the mapping? Is this connected to HAL stuff by any chance. I see references here and there to HAL but I haven’t found any doc yet. (Hey, I’m new! I’m sure there’s stuff I haven’t found yet.)
As far as I know, you can’t do it with a single read, because the “D” pins are not all connected to the same port. D0 through D4 are on GPIO port B and D5 through D7 are on port A (on the Photon). You can get a single byte of data representing D0 through D7 (D0 most significant digit) by reading both ports, masking out the parts you don’t want, and or’ing them together.
@marcus, pinReadFast() internally uses the IDR of the ports, so you would perform eight reads and multiple binary operations vs. two reads and two binary operations.
@randyenger, pinReadFast() reads the port associated with the specified GPIO pin using the IDR register. You could read multiple pins at the same time from a given port using the IDR and the correct bit mask. Then, you have to read the second port and put all the bits together. As @ScruffR points out, using pinReadFast() is the most effective way (short of having the pins on a single port). Besides, since you can read each pin very fast, you can handle each sensor input without having to logically mask each port bit.
First, many thanks for the quick replies. I now know some areas to read that I just glossed over before. And what’s already been mentioned itself is very helpful.
Second, the definitions of things like GPIOA and D7 come from somewhere, but when I tried the particle-offline-compiler, they weren’t automatically included/loaded, so things don’t compile. Where does one get these from?
Ah! Thanks. Well, hmm, tried that and I’m still getting “D7 undefined” and “unknown type name TCPServer” … But you’ve given me some ideas on things to research, so let me do that before taking up any more of your time.
