Error encountered during linking when trying to call filter function for filtering

can someone explain me a solution to the problem.

It looks like you have to include the FIR_filter.h (header) file into your .c source file.

Hello,

I don't know from where this FIR_filter.h (header) file can be found to include it.Because when I followed the instructions as mentioned here  http://www.ti.com/mcu/docs/litabsmultiplefilelist.tsp?sectionId=96&tabId=1502&literatureNumber=slaa357&docCategoryId=1&familyId=1615 it generated the files as mentioned in my first post of this thread.

So,can someone explain me about this FIR_filter.h file.

Thanks.

can someone explain me about the FIR_filter header file.

Thanks Leo Bosch,

I was able to remove the errors by following your suggestions in this 

extern FIR_filter(int);

int input_delay0; to int input_delay20;

int output = 0;

__interrupt void ADC12ISR(void)
{
 if (oldest == 499)
 {
 oldest= 0;
 }
 else
 {
 oldest=oldest+1;
 }

result=ADC12MEM0;//Store ADC12MEM0 value to result(variable)

results[oldest]=result;
input_delay0=result;
output=FIR_filter(input_delay0);
results[oldest]=output;

__bic_SR_register_on_exit(CPUOFF);
}

But I am not getting any output data when used as above which was verified by sending the results[oldest] data to the UART and it is showing results[oldest]  data on the terminal when FIR_filter is not used .

I have doubt with my FIR_filter.s43 fucntion itself (same as this except with the extension 7446.filter_CCS.txt ).

can someone explain me why this is not giving any output.

Thanks.

The FIR_filter doesn’t accept or returns parameters, just call the filter (FIR_filter();). The variable input_delay0 is input and the variable output is the output of the filter.

Hi,

I am calling the FIR_filter(); function each time I get a new ADC sample(where each ADC sample is sampled at 500Hz) as shown below but I am not getting any value into output

#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR(void)
{
	if (oldest == 499)
		{
		  oldest= 0;
		}
	else
		{
		oldest=oldest+1;
		}
	result=ADC12MEM0;
	input_delay0=result;
	FIR_filter();
	results[oldest]=output;	
	__bic_SR_register_on_exit(CPUOFF);
}

can someone help me out in solvign the problem.

stefan 12 said:

but I am not getting any value into output

There's no such thing as "no value" for variable ;) What's contents of results[], input_delay0 .. input_delayN after 500 ADC and FIR_Filter calls? Maybe your ADC is not working? Or you sample wrong input? Or signal source is not working? :)

Hi,

ADC is working fine and I checked this both with the terminal output and also with the CCS5.4 debug window.

I checked these using a break point at   results[oldest]=output;

1)Before calling FIR_filter() function the ADC sample values that are stored in results [] are showing correctly in debug window as shown in the image here 

2)when the FIR_filter() function is called , it is showing value of 0 for input_delay0 and input_delay1 ..,for the first time run in the debug window.But when it is made to run for second time it is just running in the debug window even when there is a break point as shown here and only stopping when it is stopped manually.

thanks.

I think your problem is in DC offset of your signal. FIR filtering is about AC signal processing. You can't represent AC signal using only positive values. At least not for "classic" DSP algorithms. You need to DC-shift down your ADC data so result swings around 0. If zero offset of ADC input is 1/2 of VREF, then:

result=ADC12MEM0 - 2047;

[edit] results[] shall be signed int either.

llmars,

I think FIR filtering (especially low pass) should be able to handle DC signals. Thus a DC bias shouldn't have any problem.

The bigger problem is the poster has no idea of what he is doing. He cut and past different parts of different working programs together and makes strange changes. I think part of his code is from what I did as an "example" in c for MSP430X. Some other part of his code is from the TI App Note that you suggested, which is in assembly for MSP430. I have no idea how the entire code looks like )and don't want to see it).

-- OCY