From e0afe42010efb0509e3108fa21121320d6e35b52 Mon Sep 17 00:00:00 2001
From: Hans Christian Olaussen <41271048+klutvott123@users.noreply.github.com>
Date: Wed, 27 Apr 2022 22:10:55 +0200
Subject: [PATCH] CRSF use persistent object to retain baudrate

Use persistent object to store negotiated CRSF baudrate in RTC backup register instead of .noinit.
---
 src/main/drivers/persistent.h |  1 +
 src/main/rx/crsf.c            |  4 +++-
 src/main/telemetry/crsf.c     | 10 ++++------
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/main/drivers/persistent.h b/src/main/drivers/persistent.h
index 2b7ba80b1..8dddfe175 100644
--- a/src/main/drivers/persistent.h
+++ b/src/main/drivers/persistent.h
@@ -37,6 +37,7 @@ typedef enum {
 #endif
     PERSISTENT_OBJECT_RTC_HIGH,           // high 32 bits of rtcTime_t
     PERSISTENT_OBJECT_RTC_LOW,            // low 32 bits of rtcTime_t
+    PERSISTENT_OBJECT_SERIALRX_BAUD,      // serial rx baudrate
     PERSISTENT_OBJECT_COUNT,
 #ifdef USE_SPRACING_PERSISTENT_RTC_WORKAROUND
     // On SPRACING H7 firmware use this alternate location for all reset reasons interpreted by this firmware
diff --git a/src/main/rx/crsf.c b/src/main/rx/crsf.c
index 981eb6e21..d8d9236e5 100644
--- a/src/main/rx/crsf.c
+++ b/src/main/rx/crsf.c
@@ -38,6 +38,7 @@
 
 #include "pg/rx.h"
 
+#include "drivers/persistent.h"
 #include "drivers/serial.h"
 #include "drivers/serial_uart.h"
 #include "drivers/system.h"
@@ -639,7 +640,7 @@ bool crsfRxInit(const rxConfig_t *rxConfig, rxRuntimeState_t *rxRuntimeState)
     uint32_t crsfBaudrate = CRSF_BAUDRATE;
 
 #if defined(USE_CRSF_V3)
-    crsfBaudrate = (isMPUSoftReset() && rxConfig->crsf_use_negotiated_baud) ? getCrsfCachedBaudrate() : CRSF_BAUDRATE;
+    crsfBaudrate = rxConfig->crsf_use_negotiated_baud ? getCrsfCachedBaudrate() : CRSF_BAUDRATE;
 #endif
 
     serialPort = openSerialPort(portConfig->identifier,
@@ -667,6 +668,7 @@ bool crsfRxInit(const rxConfig_t *rxConfig, rxRuntimeState_t *rxRuntimeState)
 void crsfRxUpdateBaudrate(uint32_t baudrate)
 {
     serialSetBaudRate(serialPort, baudrate);
+    persistentObjectWrite(PERSISTENT_OBJECT_SERIALRX_BAUD, baudrate);
 }
 
 bool crsfRxUseNegotiatedBaud(void)
diff --git a/src/main/telemetry/crsf.c b/src/main/telemetry/crsf.c
index 2fbb3a242..88868ce9c 100644
--- a/src/main/telemetry/crsf.c
+++ b/src/main/telemetry/crsf.c
@@ -43,6 +43,7 @@
 #include "common/utils.h"
 
 #include "drivers/nvic.h"
+#include "drivers/persistent.h"
 
 #include "fc/rc_modes.h"
 #include "fc/runtime_config.h"
@@ -103,10 +104,9 @@ typedef struct {
 
 static crsfSpeedControl_s crsfSpeed = {0};
 
-uint32_t crsfCachedBaudrate __attribute__ ((section (".noinit"))); // Used for retaining negotiated baudrate after soft reset
-
 uint32_t getCrsfCachedBaudrate(void)
 {
+    uint32_t crsfCachedBaudrate = persistentObjectRead(PERSISTENT_OBJECT_SERIALRX_BAUD);
     // check if valid first. return default baudrate if not
     for (unsigned i = 0; i < BAUD_COUNT; i++) {
         if (crsfCachedBaudrate == baudRates[i] && baudRates[i] >= CRSF_BAUDRATE) {
@@ -133,8 +133,7 @@ void setCrsfDefaultSpeed(void)
     crsfSpeed.confirmationTime = 0;
     crsfSpeed.index = BAUD_COUNT;
     isCrsfV3Running = false;
-    crsfCachedBaudrate = getCrsfDesiredSpeed();
-    crsfRxUpdateBaudrate(crsfCachedBaudrate);
+    crsfRxUpdateBaudrate(getCrsfDesiredSpeed());
 }
 
 bool crsfBaudNegotiationInProgress(void)
@@ -470,8 +469,7 @@ void speedNegotiationProcess(timeUs_t currentTimeUs)
     } else if (crsfSpeed.isNewSpeedValid) {
         if (cmpTimeUs(currentTimeUs, crsfSpeed.confirmationTime) >= 4000) {
             // delay 4ms before applying the new baudrate
-            crsfCachedBaudrate = getCrsfDesiredSpeed();
-            crsfRxUpdateBaudrate(crsfCachedBaudrate);
+            crsfRxUpdateBaudrate(getCrsfDesiredSpeed());
             crsfSpeed.isNewSpeedValid = false;
             isCrsfV3Running = true;
         }
-- 
2.11.4.GIT