posting data on wifi server example

[digistump]

After testing several solutions - including directly reading the bits (doesn't work either) - this seems to be the only working solution and explanation of why the others don't work:

http://forum.arduino.cc/index.php?topic=185291.0


also here is what I did to direct read the bits - but it only works if the pin is an input unless you do the above fix, after which digitalRead works just fine too:

inline int digitalReadDirect(int pin){
 
  int r = !!(g_APinDescription[pin].pPort -> PIO_PDSR & g_APinDescription[pin].ulPin);
 
}

[dbell]

Yep, read that. Tried it. Doesn't seem to work.
If it works, then this should toggle the LED; it sets it on and leaves it on:

int pin=13;

void setup() {
  pinMode(pin, INPUT);
  pinMode(pin, OUTPUT);
  digitalWrite(pin, LOW);
}

void loop() {
  digitalWrite(pin, !digitalRead(pin));
  delay(500);
}

[MichaelMeissner]

It sounds like the simplest solution is to use a wrapper function for digitalWrite that keeps tract of the state of the pin, and use that instead of trying to see what the entrails of the pin mapping does on the DigiX.

A simple minded approach would be:

Code: [Select]

const int max_pins = 120;
uint8_t pin_state[max_pins];

void
myDigitalWrite (uint8_t pin, uint8_t value)
{
  pin_state[pin] = value;
  digitalWrite (pin, value);
}


[dbell]

Good suggestion, Michael!
With a corresponding mydigitalRead(), it would become nearly transparent.

Thanks,

Dave

[MichaelMeissner]

If you are worried about the memory space, you could use shifting to reduce the pin state array to 1/8th the size, but given the DigiX has 96k, saving 100 bytes might not be as important as it is for the Digispark where you only have 512 bytes (0.5k).

[dbell]

Sure,

bitRead(pin_states[pin/8], pin%8);
Probably worth it for space, but the server is pretty slow, as it is...

[MichaelMeissner]

Sure,

bitRead(pin_states[pin/8], pin%8);
Probably worth it for space, but the server is pretty slow, as it is...

If you want optimal code, you want to make sure pin is an unsigned type like unsigned int, uint8_t, etc.  That way the compiler can change the /8 and %8 into LOGICAL SHIFT RIGHT/AND operations (1-2 instructions in most architectures).  The %8 on signed types involves a few extra instructions to get the sign right.

[dbell]

Good pointer - thanks!

[dbell]

I added Analog input pin display, with floating point output this morning.

Dave