Use of A/D converter

Using Arduino Project Guidance
#1

I'm doing a project and wish to use A/D converter for the input signal from my force sensor. But I got no idea how to choose a suitable ADC specially how to give clock for the ADC from arduino? output from arduino?

This is the ADC I found, and the force sensor I using: https://www.distrelec.com/ishopWebFront/search/luceneSearch.do?dispatch=find&keywordPhrase=663098 http://dshop.ch/osc/product_info.php?cPath=23_37&products_id=109375

Regards

#2

Why do you want to use that converter? It has lower resolution and is about the same speed as the built-in one.

#3

For my understanding, with the analog read in, the arduino need more processing time for the signal, but with the digital signal input will allow my arduino to run faster?

#4

Not sure what you're saying there. It is true that the existing analogRead has a busy-wait, but as I pointed out in your other thread, this is easily reduced or eliminated. You can even interrupt on the end-of-conversion condition if you wish. The converter itself does not consume processor resources.

#5

As for my system require fast feedback from the sensors so I can't afford to have such long busy-wait state. In this case I would like to try if the arduino only work with digital input allow me to have the immediate feedback from the sensors.

#6

I can’t afford to have such long busy-wait state.

So get rid of it.

analogRead, 1.0

int analogRead(uint8_t pin)
{
	uint8_t low, high;

#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
	if (pin >= 54) pin -= 54; // allow for channel or pin numbers
#elif defined(__AVR_ATmega32U4__)
	if (pin >= 18) pin -= 18; // allow for channel or pin numbers
#else
	if (pin >= 14) pin -= 14; // allow for channel or pin numbers
#endif
	
#if defined(__AVR_ATmega32U4__)
	pin = analogPinToChannel(pin);
	ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#elif defined(ADCSRB) && defined(MUX5)
	// the MUX5 bit of ADCSRB selects whether we're reading from channels
	// 0 to 7 (MUX5 low) or 8 to 15 (MUX5 high).
	ADCSRB = (ADCSRB & ~(1 << MUX5)) | (((pin >> 3) & 0x01) << MUX5);
#endif
  
	// set the analog reference (high two bits of ADMUX) and select the
	// channel (low 4 bits).  this also sets ADLAR (left-adjust result)
	// to 0 (the default).
#if defined(ADMUX)
	ADMUX = (analog_reference << 6) | (pin & 0x07);
#endif

	// without a delay, we seem to read from the wrong channel
	//delay(1);

#if defined(ADCSRA) && defined(ADCL)
	// start the conversion
	sbi(ADCSRA, ADSC);

	// ADSC is cleared when the conversion finishes
	while (bit_is_set(ADCSRA, ADSC));

	// we have to read ADCL first; doing so locks both ADCL
	// and ADCH until ADCH is read.  reading ADCL second would
	// cause the results of each conversion to be discarded,
	// as ADCL and ADCH would be locked when it completed.
	low  = ADCL;
	high = ADCH;
#else
	// we dont have an ADC, return 0
	low  = 0;
	high = 0;
#endif

	// combine the two bytes
	return (high << 8) | low;
}

Just split this into two - the setup and start conversion in one routine, and the wait and read.
Do useful work between calling them.

#7

hong89: my system require fast feedback from the sensors

What are you trying to minimise - the latency in getting the value, or the wasted processing time if your sketch waits while the conversion occurs?

#8

PeterH: What are you trying to minimise - the latency in getting the value, or the wasted processing time if your sketch waits while the conversion occurs?

I would like to minimise the latency in getting the value.

#9

Would it make sense to merge this with your other thread on the subject? I don't understand why you can't follow the advice I've already given.

#10