Merge pull request #108 from markondej/rpi4-fix

Rpi4 fix

README.md

@@ -25,11 +25,22 @@ Other options:
 * -r - Loops the playback
 
 After transmission has begun, simply tune an FM receiver to chosen frequency, You should hear the playback.
+### Raspberry Pi 4
+On Raspberry Pi 4 other built-in hardware probably interfers somehow with this software making transmitting not possible on all standard FM broadcasting frequencies. In this case it is recommended to:
+1. Compile executable with option to use GPIO21 instead of GPIO4 (PIN 40 on GPIO header):
+```
+make GPIO21=1
+```
+2. Change either ARM core frequency scaling governor settings to "performance" or to change ARM minium and maximum core frequencies to one constant value (see: https://www.raspberrypi.org/forums/viewtopic.php?t=152692 ).
+```
+echo "performance"| sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
+```
+3. Using lower FM broadcasting frequencies (below 93 MHz) when transmitting.
 ### Supported audio formats
 You can transmitt uncompressed WAV (.wav) files directly or read audio data from stdin, eg.:
 ```
 sudo apt-get install sox
-sox star_wars.wav -r 22050 -c 1 -b 16 -t wav - | sudo ./fm_transmitter -f 100.6 -
+sox acoustic_guitar_duet.wav -r 22050 -c 1 -b 16 -t wav - | sudo ./fm_transmitter -f 100.6 -
 ```
 Please note only uncompressed WAV files are supported. If you receive the "corrupted data" error try converting the file, eg. by using SoX:
 ```

main.cpp

@@ -1,7 +1,7 @@
 /*
-    fm_transmitter - use Raspberry Pi as FM transmitter
+    FM Transmitter - use Raspberry Pi as FM transmitter
 
-    Copyright (c) 2019, Marcin Kondej
+    Copyright (c) 2020, Marcin Kondej
     All rights reserved.
 
     See https://github.com/markondej/fm_transmitter
@@ -37,21 +37,21 @@
 #include <iostream>
 #include <unistd.h>
 
-bool play = true;
-Transmitter *transmitter = NULL;
+bool stop = false;
+Transmitter *transmitter = nullptr;
 
 void sigIntHandler(int sigNum)
 {
-    if (transmitter != NULL) {
+    if (transmitter != nullptr) {
         std::cout << "Stopping..." << std::endl;
-        transmitter->stop();
-        play = false;
+        transmitter->Stop();
+        stop = true;
     }
 }
 
 int main(int argc, char** argv)
 {
-    float frequency = 100.f, bandwidth = 100.f;
+    float frequency = 100.f, bandwidth = 200.f;
     uint16_t dmaChannel = 0;
     bool showUsage = true, loop = false;
     int opt, filesOffset;
@@ -87,27 +87,33 @@ int main(int argc, char** argv)
     signal(SIGINT, sigIntHandler);
     signal(SIGTSTP, sigIntHandler);
 
+    auto finally = [&]() {
+        delete transmitter;
+        transmitter = nullptr;
+    };
     try {
-        transmitter = &Transmitter::getInstance();
+        transmitter = new Transmitter();
+        std::cout << "Broadcasting at " << frequency << " MHz with "
+            << bandwidth << " kHz bandwidth" << std::endl;
         do {
             std::string filename = argv[optind++];
             if ((optind == argc) && loop) {
                 optind = filesOffset;
             }
-            WaveReader reader(filename != "-" ? filename : std::string(), play);
-            PCMWaveHeader header = reader.getHeader();
-            std::cout << "Broadcasting at " << frequency << " MHz with " 
-                << bandwidth << " kHz bandwidth" << std::endl;
-            std::cout << "Playing: " << reader.getFilename() << ", "
+            WaveReader reader(filename != "-" ? filename : std::string(), stop);
+            WaveHeader header = reader.GetHeader();
+            std::cout << "Playing: " << reader.GetFilename() << ", "
                 << header.sampleRate << " Hz, "
                 << header.bitsPerSample << " bits, "
                 << ((header.channels > 0x01) ? "stereo" : "mono") << std::endl;
-            transmitter->transmit(reader, frequency, bandwidth, dmaChannel, optind < argc);
-        } while (play && (optind < argc));
+            transmitter->Transmit(reader, frequency, bandwidth, dmaChannel, optind < argc);
+        } while (!stop && (optind < argc));
     } catch (std::exception &catched) {
         std::cout << "Error: " << catched.what() << std::endl;
+        finally();
         return 1;
     }
+    finally();
 
     return 0;
 }

makefile

@@ -1,6 +1,10 @@
 EXECUTABLE = fm_transmitter
-VERSION = 0.9.3
+VERSION = 0.9.4
 FLAGS = -Wall -O3 -std=c++11
+TRANSMITTER = -fno-strict-aliasing -I/opt/vc/include
+ifeq ($(GPIO21), 1)
+	TRANSMITTER += -DGPIO21
+endif
 
 all: main.o mailbox.o sample.o wave_reader.o transmitter.o
 	g++ -L/opt/vc/lib -lm -lpthread -lbcm_host -o $(EXECUTABLE) main.o mailbox.o sample.o wave_reader.o transmitter.o
@@ -15,7 +19,7 @@ wave_reader.o: wave_reader.cpp wave_reader.hpp
 	g++ $(FLAGS) -c wave_reader.cpp
 
 transmitter.o: transmitter.cpp transmitter.hpp
-	g++ $(FLAGS) -fno-strict-aliasing -I/opt/vc/include -c transmitter.cpp
+	g++ $(FLAGS) $(TRANSMITTER) -c transmitter.cpp
 
 main.o: main.cpp
 	g++ $(FLAGS) -DVERSION=\"$(VERSION)\" -DEXECUTABLE=\"$(EXECUTABLE)\" -c main.cpp

sample.cpp

@@ -1,7 +1,7 @@
 /*
-    fm_transmitter - use Raspberry Pi as FM transmitter
+    FM Transmitter - use Raspberry Pi as FM transmitter
 
-    Copyright (c) 2019, Marcin Kondej
+    Copyright (c) 2020, Marcin Kondej
     All rights reserved.
 
     See https://github.com/markondej/fm_transmitter
@@ -34,25 +34,27 @@
 #include "sample.hpp"
 #include <climits>
 
-Sample::Sample(uint8_t *data, uint16_t channels, uint16_t bitsPerChannel)
+Sample::Sample(uint8_t *data, unsigned channels, unsigned bitsPerChannel)
     : value(0.f)
 {
-    int32_t sum = 0;
+    int sum = 0;
     int16_t *channelValues = new int16_t[channels];
-    int16_t multiplier = bitsPerChannel >> 3;
-    for (uint32_t i = 0; i < channels; i++) {
-        if (multiplier > 1) {
-            channelValues[i] = (data[(i + 1) * multiplier - 1] << 8) | data[(i + 1) * multiplier - 2];
-        } else {
+    for (unsigned i = 0; i < channels; i++) {
+        switch (bitsPerChannel >> 3) {
+        case 2:
+            channelValues[i] = (data[((i + 1) << 1) - 1] << 8) | data[((i + 1) << 1) - 2];
+            break;
+        case 1:
             channelValues[i] = (static_cast<int16_t>(data[i]) - 0x80) << 8;
+            break;
         }
         sum += channelValues[i];
     }
-    value = 2 * sum / channels / static_cast<float>(USHRT_MAX);
+    value = 2 * sum / (static_cast<float>(USHRT_MAX) * channels);
     delete[] channelValues;
 }
 
-float Sample::getMonoValue() const
+float Sample::GetMonoValue() const
 {
     return value;
-}
+}

sample.hpp

@@ -1,7 +1,7 @@
 /*
-    fm_transmitter - use Raspberry Pi as FM transmitter
+    FM Transmitter - use Raspberry Pi as FM transmitter
 
-    Copyright (c) 2019, Marcin Kondej
+    Copyright (c) 2020, Marcin Kondej
     All rights reserved.
 
     See https://github.com/markondej/fm_transmitter
@@ -39,8 +39,8 @@
 class Sample
 {
     public:
-        Sample(uint8_t *data, uint16_t channels, uint16_t bitsPerChannel);
-        float getMonoValue() const;
+        Sample(uint8_t *data, unsigned channels, unsigned bitsPerChannel);
+        float GetMonoValue() const;
     protected:
         float value;
 };