From 314fcb2d6e9cc84696ba8d0571795eb21139b77c Mon Sep 17 00:00:00 2001
From: Jaimi5 <janms2009@gmail.com>
Date: Sun, 26 Jun 2022 23:33:05 +0200
Subject: [PATCH] RadioLib - getTimeOnAir for FSK mode in module SX127x

---
 src/modules/SX127x/SX127x.cpp | 63 +++++++++++++++++++++++------------
 1 file changed, 42 insertions(+), 21 deletions(-)

diff --git a/src/modules/SX127x/SX127x.cpp b/src/modules/SX127x/SX127x.cpp
index 5b719873..a1b18e70 100644
--- a/src/modules/SX127x/SX127x.cpp
+++ b/src/modules/SX127x/SX127x.cpp
@@ -147,7 +147,7 @@ int16_t SX127x::transmit(uint8_t* data, size_t len, uint8_t addr) {
   int16_t modem = getActiveModem();
   uint32_t start = 0;
   if(modem == RADIOLIB_SX127X_LORA) {
-    // calculate timeout (150 % of expected time-one-air)
+    // calculate timeout (150 % of expected time-on-air)
     uint32_t timeout = getTimeOnAir(len) * 1.5;
 
     // start transmission
@@ -166,7 +166,7 @@ int16_t SX127x::transmit(uint8_t* data, size_t len, uint8_t addr) {
 
   } else if(modem == RADIOLIB_SX127X_FSK_OOK) {
     // calculate timeout (5ms + 500 % of expected time-on-air)
-    uint32_t timeout = 5000000 + (uint32_t)((((float)(len * 8)) / (_br * 1000.0)) * 5000000.0);
+    uint32_t timeout = 5000 + getTimeOnAir(len) * 5;
 
     // start transmission
     state = startTransmit(data, len, addr);
@@ -218,8 +218,8 @@ int16_t SX127x::receive(uint8_t* data, size_t len) {
     }
 
   } else if(modem == RADIOLIB_SX127X_FSK_OOK) {
-    // calculate timeout (500 % of expected time-one-air)
-    uint32_t timeout = (uint32_t)((((float)(len * 8)) / (_br * 1000.0)) * 5000000.0);
+    // calculate timeout (500 % of expected time-on-air)
+    uint32_t timeout = getTimeOnAir(len) * 5;
 
     // set mode to receive
     state = startReceive(len, RADIOLIB_SX127X_RX);
@@ -1039,24 +1039,45 @@ int16_t SX127x::variablePacketLengthMode(uint8_t maxLen) {
 }
 
 uint32_t SX127x::getTimeOnAir(size_t len) {
-  // Get symbol length in us
-  float symbolLength = (float) (uint32_t(1) << _sf) / (float) _bw * 1000;
-  // Get Low Data Rate optimization flag
-  float de = 0;
-  if (symbolLength >= 16.0) {
-    de = 1;
+  // check active modem
+  uint8_t modem = getActiveModem();
+  if (modem == RADIOLIB_SX127X_LORA) {
+    // Get symbol length in us
+    float symbolLength = (float) (uint32_t(1) << _sf) / (float) _bw;
+    // Get Low Data Rate optimization flag
+    float de = 0;
+    if (symbolLength >= 16.0) {
+      de = 1;
+    }
+    // Get explicit/implicit header enabled flag
+    float ih = (float) _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_MODEM_CONFIG_1, 0, 0);
+    // Get CRC enabled flag
+    float crc = (float) (_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_MODEM_CONFIG_2, 2, 2) >> 2);
+    // Get number of bits preamble
+    float n_pre = (float) ((_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_MSB) << 8) | _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_LSB));
+    // Get number of bits payload
+    float n_pay = 8.0 + max(ceil((8.0 * (float) len - 4.0 * (float) _sf + 28.0 + 16.0 * crc - 20.0 * ih) / (4.0 * (float) _sf - 8.0 * de)) * (float) _cr, 0.0);
+
+    // Get time-on-air in us
+    return ceil(symbolLength * (n_pre + n_pay + 4.25)) * 1000;
+  } else if(modem == RADIOLIB_SX127X_FSK_OOK) {
+    // Get number of bits preamble
+    float n_pre = (float) ((_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_MSB_FSK) << 8) | _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_LSB_FSK)) * 8;
+    //Get the number of bits of the sync word
+    float n_syncWord = (float) (_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_SYNC_CONFIG, 2, 0) + 1);
+    //Get CRC enabled flag
+    float crc = (float) (_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PACKET_CONFIG_1, 4, 4) >> 2);
+    //Get payload length
+    uint16_t mode = _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PACKET_CONFIG_1, 7, 7);
+    if (mode == RADIOLIB_SX127X_PACKET_FIXED)
+      len = _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PAYLOAD_LENGTH_FSK);
+
+    // Calculate time-on-air in us ((length in bytes) * (8 bits / 1 byte)) / ((Bit Rate in kbps) * (1000 bps / 1 kbps)) * (1000000 us in 1 sec)
+    return (uint32_t) (((crc + n_syncWord + n_pre + (float) (len * 8)) / (_br * 1000.0)) * 1000000.0);
+  } else {
+    return(RADIOLIB_ERR_UNKNOWN);
   }
-  // Get explicit/implicit header enabled flag
-  float ih = (float) _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_MODEM_CONFIG_1, 0, 0);
-  // Get CRC enabled flag
-  float crc = (float) (_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_MODEM_CONFIG_2, 2, 2) >> 2);
-  // Get number of bits preamble
-  float n_pre = (float) ((_mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_MSB) << 8) | _mod->SPIgetRegValue(RADIOLIB_SX127X_REG_PREAMBLE_LSB));
-  // Get number of bits payload
-  float n_pay = 8.0 + max(ceil((8.0 * (float) len - 4.0 * (float) _sf + 28.0 + 16.0 * crc - 20.0 * ih) / (4.0 * (float) _sf - 8.0 * de)) * (float) _cr, 0.0);
-  
-  // Get time-on-air in us
-  return ceil(symbolLength * (n_pre + n_pay + 4.25));
+
 }
 
 int16_t SX127x::setCrcFiltering(bool crcOn) {