Pack and unpack using shifting and masking
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5e887a95c5
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@ -49,21 +49,17 @@ bool CFMControl::writeModem(const unsigned char* data, unsigned int length)
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for (unsigned int i = 0U; i < length; i += 3U) {
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unsigned short sample1 = 0U;
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unsigned short sample2 = 0U;
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unsigned short MASK = 0x0001U;
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unsigned short MASK = ~(0xFFFFF000);
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const unsigned char* base = data + i;
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for (unsigned int j = 0U; j < 12U; j++, MASK <<= 1) {
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unsigned int pos1 = j;
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unsigned int pos2 = j + 12U;
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int pack = 0;
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char* packPointer = (char*)&pack;
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bool b1 = READ_BIT(base, pos1) != 0U;
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bool b2 = READ_BIT(base, pos2) != 0U;
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packPointer[1] = data[i];
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packPointer[2] = data[i + 1];
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packPointer[3] = data[i + 2];
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if (b1)
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sample1 |= MASK;
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if (b2)
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sample2 |= MASK;
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}
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sample2 = (short)(pack & MASK);
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sample1 = (short)(pack >> 12);
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// Convert from unsigned short (0 - +4095) to float (-1.0 - +1.0)
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samples[nSamples++] = (float(sample1) - 2048.0F) / 2048.0F;
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@ -108,18 +104,24 @@ unsigned int CFMControl::readModem(unsigned char* data, unsigned int space)
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// Pre-emphasise the data and other stuff.
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// Pack the floating point data (+1.0 to -1.0) to packed 12-bit samples (+2047 - -2048)
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unsigned int offset = 0U;
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for (unsigned int i = 0U; i < nSamples; i++) {
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unsigned short sample = (unsigned short)((samples[i] + 1.0F) * 2048.0F + 0.5F);
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unsigned short MASK = 0x0001U;
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for (unsigned int j = 0U; j < 12U; j++, MASK <<= 1) {
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bool b = (sample & MASK) != 0U;
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WRITE_BIT(data, offset, b);
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offset++;
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}
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int pack = 0;
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char* packPointer = (char*)&pack;
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unsigned int j = 0U;
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unsigned int i = 0U;
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for (; i < nSamples && j < space; i += 2, j += 3) {
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unsigned short sample1 = (unsigned short)((samples[i] + 1.0F) * 2048.0F + 0.5F);
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unsigned short sample2 = (unsigned short)((samples[i + 1] + 1.0F) * 2048.0F + 0.5F);
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pack = 0;
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pack = ((int)sample1) << 12;
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pack |= sample2;
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data[j] = packPointer[1];
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data[j + 1] = packPointer[2];
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data[j + 2] = packPointer[3];
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}
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return nSamples;
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return j;//return the number of bytes written
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}
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void CFMControl::clock(unsigned int ms)
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11
FMControl.h
11
FMControl.h
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@ -22,6 +22,17 @@
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#include "FMNetwork.h"
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#include "Defines.h"
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typedef struct
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{
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union
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{
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int pack;
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char packBytes[4];
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};
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} SamplePack;
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class CFMControl {
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public:
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CFMControl(CFMNetwork* network);
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