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Some documentation

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This commit is contained in:
Martin Holst Swende 2015-01-26 21:15:28 +01:00
parent 7242efa07c
commit 7c676e7269
1 changed files with 25 additions and 11 deletions
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36
armsrc/lfops.c
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@ -34,7 +34,19 @@ void pushBit( BitstreamOut* stream, bool bit)
stream->position++;
stream->numbits++;
}
void DoAcquisition(int decimation, int quantization, int trigger_threshold, bool averaging)
/**
* @brief Does LF sample acquisition, this method implements decimation and quantization in order to
* be able to provide longer sample traces.
* @param decimation - how much should the signal be decimated. A decimation of 1 means every sample, 2 means
* every other sample, etc.
* @param bits_per_sample - bits per sample. Max 8, min 1 bit per sample.
* @param trigger_threshold - a threshold. The sampling won't commence until this threshold has been reached. Set
* to -1 to ignore threshold.
* @param averaging If set to true, decimation will use averaging, so that if e.g. decimation is 3, the sample
* value that will be used is the average value of the three samples.
* @return the number of bits occupied by the samples.
*/
uint8_t DoAcquisition(int decimation, int bits_per_sample, int trigger_threshold, bool averaging)
{
//A decimation of 2 means we keep every 2nd sample
//A decimation of 3 means we keep 1 in 3 samples.
@ -42,8 +54,9 @@ void DoAcquisition(int decimation, int quantization, int trigger_threshold, bool
uint8_t *dest = (uint8_t *)BigBuf;
int bufsize = BIGBUF_SIZE;
memset(dest, 0, bufsize);
// You can't decimate 8 bits more than 7 times
if(quantization > 7) quantization = 7;
if(bits_per_sample < 1) bits_per_sample = 1;
if(bits_per_sample > 8) bits_per_sample = 8;
// Use a bit stream to handle the output
BitstreamOut data = { dest , 0, 0};
int sample_counter = 0;
@ -78,19 +91,20 @@ void DoAcquisition(int decimation, int quantization, int trigger_threshold, bool
sample_sum =0;
sample_total_saved ++;
pushBit(&data, sample & 0x80);
if(quantization < 7) pushBit(&data, sample & 0x40);
if(quantization < 6) pushBit(&data, sample & 0x20);
if(quantization < 5) pushBit(&data, sample & 0x10);
if(quantization < 4) pushBit(&data, sample & 0x08);
if(quantization < 3) pushBit(&data, sample & 0x04);
if(quantization < 2) pushBit(&data, sample & 0x02);
if(quantization < 1) pushBit(&data, sample & 0x01);
if(bits_per_sample > 1) pushBit(&data, sample & 0x40);
if(bits_per_sample > 2) pushBit(&data, sample & 0x20);
if(bits_per_sample > 3) pushBit(&data, sample & 0x10);
if(bits_per_sample > 4) pushBit(&data, sample & 0x08);
if(bits_per_sample > 5) pushBit(&data, sample & 0x04);
if(bits_per_sample > 6) pushBit(&data, sample & 0x02);
if(bits_per_sample > 7) pushBit(&data, sample & 0x01);
if((data.numbits / 8) +1 >= bufsize) break;
if((data.numbits >> 3) +1 >= bufsize) break;
}
}
Dbprintf("Done, saved %l out of %l seen samples.",sample_total_saved, sample_total_numbers);
return data.numbits;
}