Support squelch in pocsag (#1415)

* Support squelch in pocsag

* Revert smooth threshold

firmware/common/dsp_iir_config.hpp

@@ -38,9 +38,7 @@ constexpr iir_biquad_config_t audio_48k_hpf_300hz_config{
 // scipy.signal.butter(2, 300 / 12000.0, 'highpass', analog=False)
 constexpr iir_biquad_config_t audio_24k_hpf_300hz_config{
     {0.94597686f, -1.89195371f, 0.94597686f},
-    {1.00000000f, -1.88903308f, 0.89487434f}
-
-};
+    {1.00000000f, -1.88903308f, 0.89487434f}};
 
 // scipy.signal.butter(2, 30 / 12000.0, 'highpass', analog=False)
 constexpr iir_biquad_config_t audio_24k_hpf_30hz_config{

firmware/common/pocsag.cpp

@@ -225,30 +225,14 @@ void pocsag_encode(const MessageType type, BCHCode& BCH_code, const uint32_t fun
     } while (char_idx < message_size);
 }
 
-// -------------------------------------------------------------------------------
-// Get the number of bits that differ between the two values.
-// -------------------------------------------------------------------------------
-inline uint8_t bitsDiff(unsigned long left, unsigned long right) {
-    unsigned long xord = left ^ right;
-    uint8_t count = 0;
-
-    for (int i = 0; i < 32; i++) {
-        if ((xord & 0x01) == 1) ++count;
-        xord = xord >> 1;
-    }
-
-    return (count);
+// ----------------------------------------------------------------------------
+// EccContainer
+// ----------------------------------------------------------------------------
+EccContainer::EccContainer() {
+    setup_ecc();
 }
 
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-static uint32_t ecs[32]; /* error correction sequence */
-static uint32_t bch[1025];
-static int eccSetup = 0;
-
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-void setupecc() {
+void EccContainer::setup_ecc() {
     unsigned int srr = 0x3b4;
     unsigned int i, n, j, k;
 
@@ -311,23 +295,12 @@ void setupecc() {
     }
 }
 
-// -------------------------------------------------------------------------------
-// -------------------------------------------------------------------------------
-inline int errorCorrection(uint32_t& val) {
-    // Set up the tables the first time
-    if (eccSetup == 0) {
-        setupecc();
-        eccSetup = 1;
-    }
-
+int EccContainer::error_correct(uint32_t& val) {
     int i, synd, errl, acc, pari, ecc, b1, b2;
 
     errl = 0;
     pari = 0;
 
-    /* run through error detection and correction routine */
-
-    // for (i=0; i<=20; i++)
     ecc = 0;
     for (i = 31; i >= 11; --i) {
         if (val & (1 << i)) {
@@ -336,7 +309,6 @@ inline int errorCorrection(uint32_t& val) {
         }
     }
 
-    // for (i=21; i<=30; i++)
     acc = 0;
     for (i = 10; i >= 1; --i) {
         acc = acc << 1;
@@ -390,8 +362,8 @@ bool pocsag_decode_batch(const POCSAGPacket& batch, POCSAGState& state) {
 
         // Error correct twice. First time to fix any errors it can,
         // second time to count number of errors that couldn't be fixed.
-        errorCorrection(codeword);
-        auto error_count = errorCorrection(codeword);
+        state.ecc->error_correct(codeword);
+        auto error_count = state.ecc->error_correct(codeword);
 
         switch (state.mode) {
             case STATE_CLEAR:

firmware/common/pocsag.hpp

@@ -56,23 +56,46 @@ enum MessageType : uint32_t {
     ALPHANUMERIC
 };
 
+/* Holds error correction arrays. This allows the arrays to
+ * be freed when POCSAG is not running, saving ~4kb of RAM. */
+class EccContainer {
+   public:
+    EccContainer();
+
+    EccContainer(const EccContainer&) = delete;
+    EccContainer(EccContainer&&) = delete;
+    EccContainer& operator=(const EccContainer&) = delete;
+    EccContainer& operator=(EccContainer&&) = delete;
+
+    int error_correct(uint32_t& val);
+
+   private:
+    void setup_ecc();
+
+    /* error correction sequence */
+    uint32_t ecs[32];
+    uint32_t bch[1025];
+};
+
 struct POCSAGState {
-    uint8_t codeword_index;
-    uint32_t function;
-    uint32_t address;
+    EccContainer* ecc = nullptr;
+    uint8_t codeword_index = 0;
+    uint32_t function = 0;
+    uint32_t address = 0;
     Mode mode = STATE_CLEAR;
     OutputType out_type = EMPTY;
-    uint32_t ascii_data;
-    uint32_t ascii_idx;
-    uint32_t errors;
-    std::string output;
+    uint32_t ascii_data = 0;
+    uint32_t ascii_idx = 0;
+    uint32_t errors = 0;
+    std::string output{};
 };
 
 const pocsag::BitRate pocsag_bitrates[4] = {
     pocsag::BitRate::FSK512,
     pocsag::BitRate::FSK1200,
     pocsag::BitRate::FSK2400,
-    pocsag::BitRate::FSK3200};
+    pocsag::BitRate::FSK3200,
+};
 
 std::string bitrate_str(BitRate bitrate);
 std::string flag_str(PacketFlag packetflag);