+typedef struct {
+ uint8_t * buffer;
+ uint32_t numbits;
+ uint8_t position;
+} BitstreamOut;
+/**
+ * @brief Pushes bit onto the stream
+ * @param stream
+ * @param bit
+ */
+void pushBit( BitstreamOut* stream, bool bit)
+{
+ int bytepos = stream->position >> 3; // divide by 8
+ int bitpos = stream->position & 7;
+ *(stream->buffer+bytepos) |= (bit & 1) << (7 - bitpos);
+ stream->position++;
+ stream->numbits++;
+}
+/**
+ * @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.
+ //A quantization of 1 means one bit is discarded from the sample (division by 2).
+ uint8_t *dest = (uint8_t *)BigBuf;
+ int bufsize = BIGBUF_SIZE;
+ memset(dest, 0, bufsize);
+ 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;
+ uint8_t sample = 0;
+ //If we want to do averaging
+ uint32_t sample_sum =0 ;
+ uint32_t sample_total_numbers =0 ;
+ uint32_t sample_total_saved =0 ;
+
+ for(;;) {
+ WDT_HIT();
+ if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_TXRDY) {
+ AT91C_BASE_SSC->SSC_THR = 0x43;
+ LED_D_ON();
+ }
+ if (AT91C_BASE_SSC->SSC_SR & AT91C_SSC_RXRDY) {
+ sample = (uint8_t)AT91C_BASE_SSC->SSC_RHR;
+ if (trigger_threshold != -1 && sample < trigger_threshold)
+ continue;
+ sample_total_numbers++;
+
+ LED_D_OFF();
+ trigger_threshold = -1;
+ sample_counter++;
+ sample_sum += sample;
+ //Check decimation
+ if(sample_counter < decimation) continue;
+ //Averaging
+ if(averaging) sample = sample_sum / decimation;
+
+ sample_counter = 0;
+ sample_sum =0;
+ sample_total_saved ++;
+ pushBit(&data, sample & 0x80);
+ 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 >> 3) +1 >= bufsize) break;
+ }
+ }
+ Dbprintf("Done, saved %l out of %l seen samples.",sample_total_saved, sample_total_numbers);
+
+ return data.numbits;
+}
+