fast digital read

[cosmok82]

Hi. I'd like to read raw data on a specific port for a more fast digital input from this port.

My intention is to decode an ir signal with code, but digitalRead(IRpin) (IRpin = a fixed pin) is too much slow.

I inspire my project on this code http://learn.adafruit.com/trinket-gemma-ir-remote-control/using-ir-codes , but I don't know which is the port manipulation, such as IRpin_PIN & _BV(IRpin), in energia for a Stellaris Launchpad.

Do you have any solutions?

[rei-vilo]

For the Stellaris now Tiva C Series, the topic has been discussed and solved based on HWREG on the 43oh and Stellarisiti forums.

[cosmok82]

For Stellaris Launchpad LM8F120, excuse me.

[cosmok82]

I answer me by myself. I haven't tested in-depth the code still now, but I think that it work.

On top I include this for the device:

#include "inc/lm4f120h5qr.h"

// IRpin = PB_5;
#define IRpin GPIOPinRead(GPIO_PORTB_BASE, 0x20)

Then in setup() I put this lines:

// setting of PORTB on only pin 5 (0x20), fixed to 2mA (_2MA), with pull-up (_STD)
GPIOPadConfigSet(GPIO_PORTB_BASE, 0x20, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_STD);

And I used this construction to check the bit "0" and "1" in input on port: while (! IRpin ){ ... } ; while ( IRpin ){ ... }

I think that it's all right :)

[cosmok82]

rei-vilo I ask your help. This is my code; I applied the rules for a fast reading, but even with these I get an strange/failed reading of port.

You has closed this issue, but could you answer me about?

#include "inc/lm4f120h5qr.h"

// IRpin = PB_5
#define IRpin GPIOPinRead(GPIO_PORTB_BASE, 0x20)

const int MAXPULSE =  5000; // the maximum pulse we'll listen for - 5 milliseconds
const int NUMPULSES =  100; // max IR pulse pairs to sample
const int RESOLUTION =   1; // time between IR measurements

// we will store up to 100 pulse pairs (this is -a lot-)
uint16_t pulses[100][2];   // pair is high and low pulse
uint16_t currentpulse = 0; // index for pulses we're storing
uint32_t irCode = 0;

void setup(void) {

  // setting of PORTB on only pin 5 (0x20), fixed to 2mA (_2MA), with open-drain (_OD)
  GPIOPadConfigSet(GPIO_PORTB_BASE, 0x20, GPIO_STRENGTH_2MA, GPIO_PIN_TYPE_OD);

  Serial.begin(9600);
  Serial.println("Ready to decode IR!");
}

void loop(void) {

  uint16_t numpulse = listenForIR(); // Wait for an IR Code

  // Process the pulses to get a single number representing code
  for (int i = 0; i < 32; i++) {
    irCode = irCode << 1;
    if((pulses[i][0] * RESOLUTION)>0 && (pulses[i][0] * RESOLUTION)<500) {
      // leave the "0" 
    } else {
      irCode++; // add an "1"
    }
  }

  printcode();  // Print IR code to softwareserial

}

void printcode(void) {

  uint16_t half;
  half = irCode >> 16;  // Get first 16 bits of code
  Serial.print(half ^ 0xFFFF, HEX);  // Print upper inverted 16 bits in hex
  Serial.print(' ');
  Serial.println((irCode & 0xFFFF) ^ 0xFFFF, HEX); // Print lower inverted 16 bits in hex
}

uint16_t listenForIR() {  // IR receive code

  currentpulse = 0;
  while (1) {
   unsigned int highpulse, lowpulse;  // temporary storage timing
   highpulse = lowpulse = 0; // start out with no pulse length 

   // read IRpin "1" input
   while ( IRpin ){
      highpulse++; 
      delayMicroseconds(RESOLUTION);
      if (((highpulse >= MAXPULSE) && (currentpulse != 0))|| currentpulse == NUMPULSES) {
        return currentpulse; 
      }
   }
   pulses[currentpulse][0] = highpulse;

   // read IRpin "0" input
   while (! IRpin ){
      lowpulse++; 
      delayMicroseconds(RESOLUTION);
      if (((lowpulse >= MAXPULSE) && (currentpulse != 0))|| currentpulse == NUMPULSES) {
        return currentpulse; 
      }
   }
   pulses[currentpulse][1] = lowpulse;

   currentpulse++;
  }
}

[rei-vilo]

For fast digital reason pin PB_7, we need to

• first declare those macros

#define LCD_DATAH_PERIPH        SYSCTL_PERIPH_GPIOB
#define LCD_DATAH_BASE          GPIO_PORTB_BASE
#define LCD_DATAH_PINS          GPIO_PIN_7

• then define BP_7 as input

GPIOPinTypeGPIOInput(LCD_DATAH_BASE, GPIO_PIN_7);

• and finally read the value

result = HWREG(LCD_DATAH_BASE + GPIO_O_DATA + (LCD_DATAH_PINS << 2));

Hope that helps!