Using ADC to interrupt and write to memory buffer

# 09 Aug 2011

I'm trying to use the example2.h code from the MODDMA library to sample an ADC at 100Hz for 15 sec. After the first sample, I need to progress to the next on the buffer and delete the previous one. My code is below, and the interrupts work, the sampling works, but I can't progress through the buffer for the next sample. I think it's either a logic error, or a command like nextLLI.

    while (1)  {
        if (dmaTransferComplete || counter>0) {

            int i, value, channel;

            if (counter ==1500) {
                int write = 0;
                led1 = 1;
                d = opendir("/sd/data"); //open the directory for data storage. If non existant, create

                FILE *fp = fopen("/sd/Data/triax.txt", "a");//confirm can access text file for saving. If not there, create
                if (fp == NULL) {
                    error("Could not open file for write\n");
                }

                while (write<1500) {
                    write++;
                    for (i = 0; i < 3; i++) {

                        value = (adBuffer[i] >> 4) & 0xFFF;
                        channel = (adBuffer[i] >> 24) & 0x3;
                        channel--;
                        if (channel == -1) channel = 2; // Workaround ch num problem.
                        double fVal = 3.3 * (double)((double)value) / ((double)0x1000); // scale to 0v to 3.3v
         
                        if (channel != 2) {
                            fprintf(fp,"%01.3f\t", fVal);
                            fflush(stdout);
                        }
                        if (channel == 2) {
                            fprintf(fp,"%01.3f\n", fVal);
                            fflush(stdout);
                        }

                        counter--;
                        c++;

                    }
                }
            }
            fclose(fp);//close file and stop accessing SD card
            led1 = 0;
        }
        dmaTransferComplete = false;
    }

I'm trying to use the example2.h code from the MODDMA library to sample an ADC at 100Hz for 15 sec. After the first sample, I need to progress to the next on the buffer and delete the previous one. My code is below, and the interrupts work, the sampling works, but I can't progress through the buffer for the next sample. I think it's either a logic error, or a command like nextLLI. <<code>> while (1) { if (dmaTransferComplete || counter>0) { int i, value, channel; if (counter ==1500) { int write = 0; led1 = 1; d = opendir("/sd/data"); //open the directory for data storage. If non existant, create FILE *fp = fopen("/sd/Data/triax.txt", "a");//confirm can access text file for saving. If not there, create if (fp == NULL) { error("Could not open file for write\n"); } while (write<1500) { write++; for (i = 0; i < 3; i++) { value = (adBuffer[i] >> 4) & 0xFFF; channel = (adBuffer[i] >> 24) & 0x3; channel--; if (channel == -1) channel = 2; // Workaround ch num problem. double fVal = 3.3 * (double)((double)value) / ((double)0x1000); // scale to 0v to 3.3v if (channel != 2) { fprintf(fp,"%01.3f\t", fVal); fflush(stdout); } if (channel == 2) { fprintf(fp,"%01.3f\n", fVal); fflush(stdout); } counter--; c++; } } } fclose(fp);//close file and stop accessing SD card led1 = 0; } dmaTransferComplete = false; } <</code>>

Andrew Harpin

# 13 Aug 2011

Change the counter == 1500 to counter >= 1500.

Counter is incremented externally and so the value can be greater than.

Andrew Cook

# 15 Aug 2011

Andrew Harpin wrote:

Change the counter == 1500 to counter >= 1500.

Counter is incremented externally and so the value can be greater than.

Thanks Andrew, I missed that one. However I can get into the while loop, but the buffer doesn't progress to the next sample for 5 loops. I think it's because I'm not actually popping, but not 100% sure on how to do it.

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