/* ReceiverPart2.ino Bob Larkin 29 April 2020 * This is a simple DSP radio design. It can receive 2 modes, * Single Sideband (SSB) and Narrow Band FM (NBFM). SSB * breaks into Lower Sidband (LSB) and Upper Sideband (USB). * It gets even better in that AM can be received on either * LSB or USB by tuning to the AM carrier frequency. * * The signal path is switched between SSB and FM by a Chip * Audette AudioSwitch4_F32 switch block. This keeps resources * from being used in blocks that are not needed. * * We are restricted to receiving in the 8 to 22 kHz range, * so to use this on the air would require frequency conversion * hardware. * * Details on the blocks are part of the include .h files for the * blocks and in the INO files * TestFM.ino * ReceiverPart1.ino * * Input and Output is via the Teensy Audio Adaptor that uses * a SGTL5000 CODEC, * * See the individual .h files for each block for more details. * * Measured peak-to-peak levels, using AudioAnalyzePeak_F32, * all done at overload point for ADC: * At ADC (i2sIn), max, 2.0 * At IQ Mixer out, max, 2.0 * At 90 deg Phase out, 2.0 * At Sum out 2.0 * At LPF FIR Out 2.0 * * FM Det gives 0.50 out for about 5.6 kHz p-p deviation * * With a 14 kHz input sine wave, 0.5 Vp-p the LSB output is 0.738 p-p * With 15kHz, 1000Hz FM modulation, 2 kHz deviation, NBFM output is 0.173 p-p * * T3.6 Processor load, measured: 17% for NBFM * 31% for LSB or USB, 29 tap LPF * T4.0 Processor load, measured: 4.3% for NBFM * 6.5% for LSB or USB, 29 tap LPF */ #include "Audio.h" #include // *********** Mini Control Panel ************ // Set mode and gain here and re-compile // Here is the mode switch #define LSB 1 #define USB 2 #define NBFM 3 uint16_t mode = LSB; // <--Select mode int gainControlDB = 0; // <--Set SSB gain in dB. // ********************************************************* // To work with T4.0 the I2S routine outputs 16-bit integer (I16). Then // use Audette I16 to F32 convert. Same below for output, in reverse. AudioInputI2S i2sIn; AudioConvert_I16toF32 cnvrt1; AudioSwitch4_OA_F32 switch1; // Select SSB or FM RadioIQMixer_F32 iqmixer1; AudioFilter90Deg_F32 hilbert1; AudioMixer4_F32 sum1; // Summing node for the SSB receiver AudioFilterFIR_F32 fir1; // Low Pass Filter to frequency limit the SSB RadioFMDetector_F32 fmdet1; // NBFM from 10 to 20 kHz AudioMixer4_F32 sum2; // SSB and NBFM rejoin here AudioConvert_F32toI16 cnvrt2; // Left AudioConvert_F32toI16 cnvrt3; // Right AudioAnalyzePeak_F32 peak1; AudioOutputI2S i2sOut; AudioControlSGTL5000 sgtl5000_1; AudioConnection conI16_1(i2sIn, 0, cnvrt1, 0); // ADC AudioConnection_F32 connect0(cnvrt1, 0, switch1, 0); // Analog to Digital AudioConnection_F32 connect1(switch1, 0, iqmixer1, 0); // SSB Input AudioConnection_F32 connect2(switch1, 0, iqmixer1, 1); // SSB Input AudioConnection_F32 connect3(switch1, 1, fmdet1, 0); // FM input AudioConnection_F32 connect4(iqmixer1, 0, hilbert1, 0); // Broadband 90 deg phase AudioConnection_F32 connect5(iqmixer1, 1, hilbert1, 1); AudioConnection_F32 connect6(hilbert1, 0, sum1, 0); // Sideband select AudioConnection_F32 connect7(hilbert1, 1, sum1, 1); AudioConnection_F32 connect8(sum1, 0, fir1, 0); // Limit audio SSB BW AudioConnection_F32 connect9(fir1, 0, sum2, 0); // Output of SSB <<9 kHz, -62 dB, 29 taps */ float32_t fir_IQ29[29] = { -0.000970689f, -0.004690292f, -0.008256345f, -0.007565650f, 0.001524420f, 0.015435011f, 0.021920240f, 0.008211937f, -0.024286413f, -0.052184700f, -0.040532507f, 0.031248107f, 0.146902412f, 0.255179564f, 0.299445269f, 0.255179564f, 0.146902412f, 0.031248107f, -0.040532507f, -0.052184700f, -0.024286413f, 0.008211937f, 0.021920240f, 0.015435011f, 0.001524420f, -0.007565650f, -0.008256345f, -0.004690292f, -0.000970689f}; void setup(void) { float32_t vGain; AudioMemory(10); AudioMemory_F32(10); Serial.begin(300); delay(1000); // Enable the audio shield, select input, and enable output sgtl5000_1.enable(); // ADC sgtl5000_1.inputSelect(AUDIO_INPUT_LINEIN); // The switch is single pole 4 position, numbered (0, 3) 0=SSB, 1 = FM if(mode==LSB || mode==USB){ switch1.setChannel(0); Serial.println("SSB"); } else if(mode==NBFM) { switch1.setChannel(1); Serial.println("NBFM"); } iqmixer1.frequency(15000.0); // LO Frequency, typically 10 to 15 kHz hilbert1.begin(hilbert251A, 251); // Set the Hilbert transform FIR filter sum1.gain(0, 1.0f); // Leave set at 1.0 if(mode==LSB) sum1.gain(1, -1.0f); // -1 for LSB out else if(mode==USB) sum1.gain(1, 1.0f); // +1 for USB and for NBFM, we don't care // The FM detector has error checking during object construction // when Serial.print is not available. See RadioFMDetector_F32.h: Serial.print("FM Initialization errors: "); Serial.println( fmdet1.returnInitializeFMError() ); // The following enables error checking inside of the "ubdate()" // Output goes to the Serial (USB) Monitor. Normally, this is quiet. if (mode == NBFM) fmdet1.showError(1); // See RadioFMDetector_F32.h for information on functions for modifying the // FM Detector. Default values are used here, starting with a 15 kHz center frequency. fir1.begin(fir_IQ29, 29); // 5 kHz bandwidth set for radio in SSB // The gainControlDB goes in 1 dB steps. Convert here to a voltage ratio vGain = powf(10.0f, ((float32_t)gainControlDB)/20.0 ); // And apply that ratio to the output summing block. Gain here for SSB only sum2.gain(0, vGain); Serial.print("SSB vGain = "); Serial.println(vGain, 4); sum2.gain(2, 1.0f); // FM gain // The following enable error checking inside of the blocks indicated. // Output goes to the Serial (USB) Monitor. Use for debug. //hilbert1.showError(1); // Should show input error when in FM //fmdet1.showError(1); // Should show input error when in LSB or USB } void loop(void) { if (peak1.available() ) { Serial.print("P-P ="); Serial.println(peak1.readPeakToPeak(), 6); } else Serial.println("Peak-Peak not available"); Serial.print("CPU: Percent Usage, Max: "); Serial.print(AudioProcessorUsage()); Serial.print(", "); Serial.println(AudioProcessorUsageMax()); Serial.print("Int16 Memory: "); Serial.print(AudioMemoryUsage()); Serial.print(", "); Serial.println(AudioMemoryUsageMax()); Serial.print("Float 32 Memory: "); Serial.print(AudioMemoryUsage_F32()); Serial.print(", "); Serial.println(AudioMemoryUsageMax_F32()); delay(1000); }