Help with code creation for ADuC847 in C

The design of your software really needs improvement. Of course you can use an interrupt service routine (ISR) to collect the result of the ADC. However, the execution time of an ISR should be as short as possible. Therefore you usually don't use printf in an ISR and for sure not a delay function for 1 second. An ISR should read the ADC result from the ADC register into a buffer and leave. If the measurements with the ADC should be so slow, why don't you do this in your main function? I don't see a reason for an ISR

Here are some general answers to your questions. I did not check the values you write into registers and I did not try your application on a board.

mknoob11 said:

If someone could advise me on how to reduce the x,y,z outputs from 6 to 5, hopefully without causing inaccurate readings, that would be great.

Since the ADC of the ADuC847 has a 24 bit accuracy, there will be a loss of precision if you reduce the output from 6 hex digits to 5. In order to strip off the least significant 4 bits (1 digit), I would write:

printf("A%bX%bX%bX",ADC0H,ADC0M,(ADC0L >> 4));

mknoob11 said:

The other issue I'm having is that I am struggling with turning on the other analog inputs of the device, or if I turn them on, its displaying the same measurement three times. The code that I have placed below is very basic, and was started with the example code that came with the software.

The way you have written your code (3 subsequent printf lines) will of course output the same values. You need to select a different input channel, start a ADC conversion and then you can read the ADC0H, ADC0M and ADC0L register again.

mknoob11 said:

I've also tried to write a delay program, but insofar I've only got it to freeze after outputting the string.

A delay in a ISR??? Please see my comment above.
I don't know why your delay function acts like an endless loop. Usually it should only delay the program by a few cycles.

mknoob11 said:

The code doesn't include an attempt to turn on the other analog inputs, I originally tried it in using only ASM51, but have since switched to C and am not sure how to proceed with accomplishing that task.

You need to fix your program structure first. I would use the following structure (pseudo code):

}

main {
  initialize_UART();
  initialize_ADC();
  while(1) {
    Select_Channel(0);
    StartADC();
    Wait_for_ADC_conversion();
    val1 = ReadADC();
    Select_Channel(1);
    StartADC();
    Wait_for_ADC_conversion();
    val2 = ReadADC();
    Select_Channel(2);
    StartADC();
    Wait_for_ADC_conversion();
    val3 = ReadADC();
    Printf(val1,val2,val3);
    Additional_Delay_if_necessary();
  }
}

The design of your software really needs improvement. Of course you can use an interrupt service routine (ISR) to collect the result of the ADC. However, the execution time of an ISR should be as short as possible. Therefore you usually don't use printf in an ISR and for sure not a delay function for 1 second. An ISR should read the ADC result from the ADC register into a buffer and leave. If the measurements with the ADC should be so slow, why don't you do this in your main function? I don't see a reason for an ISR

Here are some general answers to your questions. I did not check the values you write into registers and I did not try your application on a board.

mknoob11 said:

If someone could advise me on how to reduce the x,y,z outputs from 6 to 5, hopefully without causing inaccurate readings, that would be great.

Since the ADC of the ADuC847 has a 24 bit accuracy, there will be a loss of precision if you reduce the output from 6 hex digits to 5. In order to strip off the least significant 4 bits (1 digit), I would write:

printf("A%bX%bX%bX",ADC0H,ADC0M,(ADC0L >> 4));

mknoob11 said:

The other issue I'm having is that I am struggling with turning on the other analog inputs of the device, or if I turn them on, its displaying the same measurement three times. The code that I have placed below is very basic, and was started with the example code that came with the software.

The way you have written your code (3 subsequent printf lines) will of course output the same values. You need to select a different input channel, start a ADC conversion and then you can read the ADC0H, ADC0M and ADC0L register again.

mknoob11 said:

I've also tried to write a delay program, but insofar I've only got it to freeze after outputting the string.

A delay in a ISR??? Please see my comment above.
I don't know why your delay function acts like an endless loop. Usually it should only delay the program by a few cycles.

mknoob11 said:

The code doesn't include an attempt to turn on the other analog inputs, I originally tried it in using only ASM51, but have since switched to C and am not sure how to proceed with accomplishing that task.

You need to fix your program structure first. I would use the following structure (pseudo code):

}

main {
  initialize_UART();
  initialize_ADC();
  while(1) {
    Select_Channel(0);
    StartADC();
    Wait_for_ADC_conversion();
    val1 = ReadADC();
    Select_Channel(1);
    StartADC();
    Wait_for_ADC_conversion();
    val2 = ReadADC();
    Select_Channel(2);
    StartADC();
    Wait_for_ADC_conversion();
    val3 = ReadADC();
    Printf(val1,val2,val3);
    Additional_Delay_if_necessary();
  }
}

Your suggestions have been immensely helpful! I've taken a lot of your pseudo code, and turned them into functions. There are a few problems I'm still having, and so I have a few more questions if you don't mind:

1. For starting the ADC, that is done by simply placing a value into the ADCMODE register correct? When I change the analog channel that I'm reading from do I really need to reenable the ADCMODE again? I figured it would still be converting, but just from a different channel now. Here's the code that I have that enables which port I want to read from, and starts the conversions:

void selectChannel1()
{
	ADC0CON2 = 0x40;
	ADCMODE = 0x23; //ADC enabled, CHOP enabled, continuous conversion
}

void selectChannel2()
{
	ADC0CON2 = 0x81;
	ADCMODE = 0x23; //ADC enabled, CHOP enabled, continuous conversion
}

void selectChannel5()
{
	ADC0CON2 = 0x04;
	ADCMODE = 0x23; //ADC enabled, CHOP enabled, continuous conversion
}

My next question is about buffering the data from these inputs. I'm unsure of how to get that done, I've programmed the register ADC0CON1 to be a full buffer, Unipolar, 2.56V, but I'm sure there's more to it. Could you point me in the right direction here?

Your suggestion for using the (ADC0L >> 4) command was a godsend. I've posted my code below with descriptions of what's going on:

This is the main body of the code, I've been slowly including functions as I figure out how to create them, and the ones that still need work are commented out:

sbit LED = 0x0B4;

void main (void)
{
	//Configure the board to communicate 115200 baud
	baud();
	
	//Initialize the ADC
	ADC();
	
	while(1)
	{
		printf("\n\n");
		selectChannel1();	//selects which pin to read analog signals from.
		//startADC();
		//wait_for_ADC_conversion();
		//Place data in buffer
		printf("A%bX%bX%bX",ADC0H,ADC0M,(ADC0L >> 4)); //prints Axxxxx data
		selectChannel2();
		//startADC();
		//wait_for_ADC_conversion();
		//place data in buffer
		printf("B%bX%bX%bX",ADC0H,ADC0M,(ADC0L >> 4)); //prints Byyyyy data
		selectChannel5();
		//startADC();
		//wait_for_ADC_conversion();
		//place data in buffer
		//send data packet
		printf("C%bX%bX%bX",ADC0H,ADC0M,(ADC0L >> 4)); //prints Czzzzz data
		delay(150);	//~1 sec delay
	}

This is the function that sets my baud rate to 115200:

void baud ()
{
	PLLCON = 0x90;
	T3CON = 0x82;
	T3FD = 0x2D;
	SCON = 0x52;
}
	

This function initializes the ADC:

void ADC()
{
	ICON = 0x01; 	//Turn on IEXC1 source to drive RTD
	SF = 0x45;		//Initialize the special function registers
	ADC0CON1 = 27;//Full Buffer, Bipolar, +/-2.56V range	
	EADC = 1;		//Enable ADC Interrupt
	EA = 1;			//Enable Global Interrupts
	//ADCMODE = 0x23; //ADC enabled, CHOP enabled, continuous conversion
}

Again, thanks for any and all help you may provide!

mknoob11 said:

1. For starting the ADC, that is done by simply placing a value into the ADCMODE register correct?

I did not read the manual of this device in detail, but I think you are right. However, in your functions 'selectChannel1/2/5' you select the right channel, but different reference voltages. Do you do this intentionally? Directly after these functions are left, you output the values with a printf. This will for sure not work, because the ADC will need time for the conversion. You should check the RDY0 in the ADCSTAT register if the ADC has finished the conversion.

mknoob11 said:

When I change the analog channel that I'm reading from do I really need to reenable the ADCMODE again?

Yes, I think so, but I'm not an expert for this ADC.

mknoob11 said:

This function initializes the ADC:

In this function you enable the interrupt for the ADC. I think this is wrong because your don't use ISRs to collect the values.

mknoob11 said:

My next question is about buffering the data from these inputs. I'm unsure of how to get that done,

What I meant is that you should read the ADC0H/M/L registers when the conversion is completed and copy these values into local or global variables before you start the next conversion. This way, the values are consistent before you output them via printf.

Thanks! I've reworked the code and got it almost perfect! There are a few issues I'm still having, but I have some potential solutions before coming here for more questions. The delays between the data acquisitions worked flawlessly, and I've made sure that the delay is long enough to allow for the conversion to be completed. Thanks again for your help.