From 6b1cd88eff3b68b5472460622bdc86bb13d76298 Mon Sep 17 00:00:00 2001
From: 3djc <5167938+3djc@users.noreply.github.com>
Date: Wed, 28 Jan 2026 07:06:06 +0100
Subject: [PATCH] fix(f4): limit CRSF external module speed to 3.75Mbps (#6923)

Co-authored-by: elecpower <elecpower@users.noreply.github.com>
---
 companion/src/firmwares/boards.h              |  5 ++
 .../src/firmwares/edgetx/yaml_modeldata.cpp   |  6 ++
 companion/src/firmwares/moduledata.cpp        |  6 +-
 companion/src/firmwares/moduledata.h          |  2 +-
 companion/src/modeledit/setup_module.cpp      |  9 +-
 companion/src/modeledit/setup_module.ui       | 90 ++++++++++---------
 .../colorlcd/module/crossfire_settings.cpp    |  2 +-
 radio/src/storage/storage_common.cpp          |  8 ++
 radio/src/telemetry/crossfire.h               |  6 ++
 9 files changed, 86 insertions(+), 48 deletions(-)

diff --git a/companion/src/firmwares/boards.h b/companion/src/firmwares/boards.h
index 7d595a2dc..696283837 100644
--- a/companion/src/firmwares/boards.h
+++ b/companion/src/firmwares/boards.h
@@ -859,3 +859,8 @@ inline bool IS_STM32H7(Board::Type board)
          IS_JUMPER_T15PRO(board) ||
          IS_RADIOMASTER_TX15(board);
 }
+
+inline bool IS_STM32F2F4(Board::Type board)
+{
+  return (!IS_STM32H5(board) && !IS_STM32H7(board));
+}
diff --git a/companion/src/firmwares/edgetx/yaml_modeldata.cpp b/companion/src/firmwares/edgetx/yaml_modeldata.cpp
index c1db7a7b4..1c76b52da 100644
--- a/companion/src/firmwares/edgetx/yaml_modeldata.cpp
+++ b/companion/src/firmwares/edgetx/yaml_modeldata.cpp
@@ -1504,6 +1504,12 @@ bool convert<ModelData>::decode(const Node& node, ModelData& rhs)
     rhs.moduleData[i].modelId = modelIds[i];
   }
 
+  // v2.12 CRSF limit external module to 3.75M for older boards
+  if (IS_STM32F2F4(board) &&
+      rhs.moduleData[1].protocol == PULSES_CROSSFIRE &&
+      rhs.moduleData[1].crsf.telemetryBaudrate > 4)
+    rhs.moduleData[1].crsf.telemetryBaudrate = 4;
+
   if (node["failsafeChannels"]) {
     int failsafeChans[CPN_MAX_CHNOUT];
     memset(failsafeChans, 0, sizeof(failsafeChans));
diff --git a/companion/src/firmwares/moduledata.cpp b/companion/src/firmwares/moduledata.cpp
index 78a5e103c..d8fcf3589 100644
--- a/companion/src/firmwares/moduledata.cpp
+++ b/companion/src/firmwares/moduledata.cpp
@@ -641,12 +641,16 @@ AbstractStaticItemModel * ModuleData::protocolItemModel(GeneralSettings & settin
   return mdl;
 }
 
-AbstractStaticItemModel * ModuleData::telemetryBaudrateItemModel(unsigned int  protocol)
+AbstractStaticItemModel * ModuleData::telemetryBaudrateItemModel(unsigned int protocol, int moduleIdx, int board)
 {
   AbstractStaticItemModel * mdl = new AbstractStaticItemModel();
   mdl->setName("moduledata.baudrate");
 
   for (int i = 0; i < moduleBaudratesList.size(); i++) {
+    // CRSF limit external module to 3.75M for older boards
+    if (protocol == PULSES_CROSSFIRE && moduleIdx == 1 &&
+        IS_STM32F2F4((Board::Type)board) && i > 4) break;
+
     if (protocol == PULSES_GHOST && i >= 2) break;
     mdl->appendToItemList(moduleBaudratesList.at(i), i);
   }
diff --git a/companion/src/firmwares/moduledata.h b/companion/src/firmwares/moduledata.h
index 0b86f59d3..fea3c14c8 100644
--- a/companion/src/firmwares/moduledata.h
+++ b/companion/src/firmwares/moduledata.h
@@ -235,7 +235,7 @@ class ModuleData {
     static AbstractStaticItemModel * internalModuleItemModel(int board = -1);
     static bool isProtocolAvailable(int moduleidx, unsigned int  protocol, GeneralSettings & generalSettings);
     static AbstractStaticItemModel * protocolItemModel(GeneralSettings & settings);
-    static AbstractStaticItemModel * telemetryBaudrateItemModel(unsigned int protocol);
+    static AbstractStaticItemModel * telemetryBaudrateItemModel(unsigned int protocol, int moduleIdx = -1, int board = 0);
     static bool isAvailable(PulsesProtocol proto, int port = 0);  //  moved from OpenTxFirmware EdgeTX v2.9 - TODO remove and use isProtocolAvailable
 
     QString afhds2aMode1ToString() const;
diff --git a/companion/src/modeledit/setup_module.cpp b/companion/src/modeledit/setup_module.cpp
index 25ce12bcd..9815ff293 100644
--- a/companion/src/modeledit/setup_module.cpp
+++ b/companion/src/modeledit/setup_module.cpp
@@ -352,7 +352,7 @@ void ModulePanel::update()
       case PULSES_CROSSFIRE:
         mask |= MASK_CHANNELS_RANGE | MASK_RX_NUMBER | MASK_BAUDRATE | MASK_CSRF_ARMING_MODE;
         module.channelsCount = 16;
-        ui->telemetryBaudrate->setModel(ModuleData::telemetryBaudrateItemModel(protocol));
+        ui->telemetryBaudrate->setModel(ModuleData::telemetryBaudrateItemModel(protocol, moduleIdx, board));
         ui->telemetryBaudrate->setField(module.crsf.telemetryBaudrate);
         ui->crsfArmingMode->setCurrentIndex(module.crsf.crsfArmingMode);
         if (module.crsf.crsfArmingMode == ModuleData::CRSF_ARMING_MODE_SWITCH) {
@@ -428,10 +428,13 @@ void ModulePanel::update()
     mask |= MASK_PPM_FIELDS | MASK_CHANNELS_RANGE | MASK_CHANNELS_COUNT;
   }
 
-  if (isExternalModule(moduleIdx))
+  if (isExternalModule(moduleIdx)) {
+    ui->label_baudrate->setVisible(mask & MASK_BAUDRATE);
     ui->telemetryBaudrate->setVisible(mask & MASK_BAUDRATE);
-  else
+  } else {
+    ui->label_baudrate->setVisible(false);
     ui->telemetryBaudrate->setVisible(false);
+  }
 
   ui->label_protocol->setVisible(mask & MASK_PROTOCOL);
   ui->protocol->setVisible(mask & MASK_PROTOCOL);
diff --git a/companion/src/modeledit/setup_module.ui b/companion/src/modeledit/setup_module.ui
index 94cc274b7..afefaf097 100644
--- a/companion/src/modeledit/setup_module.ui
+++ b/companion/src/modeledit/setup_module.ui
@@ -35,7 +35,7 @@
    <item>
     <widget class="Line" name="line">
      <property name="orientation">
-      <enum>Qt::Horizontal</enum>
+      <enum>Qt::Orientation::Horizontal</enum>
      </property>
     </widget>
    </item>
@@ -49,7 +49,6 @@
      </property>
      <property name="font">
       <font>
-       <weight>75</weight>
        <bold>true</bold>
       </font>
      </property>
@@ -94,7 +93,7 @@
       <item row="2" column="0" colspan="3">
        <spacer name="verticalSpacer">
         <property name="orientation">
-         <enum>Qt::Vertical</enum>
+         <enum>Qt::Orientation::Vertical</enum>
         </property>
         <property name="sizeHint" stdset="0">
          <size>
@@ -107,7 +106,7 @@
       <item row="0" column="0">
        <layout class="QFormLayout" name="formLayout_col1">
         <property name="labelAlignment">
-         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+         <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
         </property>
         <property name="horizontalSpacing">
          <number>6</number>
@@ -127,7 +126,7 @@
            <string>Protocol</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -146,14 +145,14 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
         <item row="1" column="1">
          <widget class="AutoComboBox" name="telemetryBaudrate">
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -163,7 +162,7 @@
            <string>Registration ID</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -183,7 +182,7 @@
            <string>Multi Radio Protocol</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -202,7 +201,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -228,7 +227,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -288,7 +287,7 @@
            <string>Failsafe Mode</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -307,7 +306,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
           <item>
            <property name="text">
@@ -348,7 +347,7 @@
            <string>Trainer Mode</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -367,7 +366,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -402,7 +401,7 @@
         <item row="17" column="0" colspan="2">
          <spacer name="horizontalSpacer_3">
           <property name="orientation">
-           <enum>Qt::Horizontal</enum>
+           <enum>Qt::Orientation::Horizontal</enum>
           </property>
           <property name="sizeHint" stdset="0">
            <size>
@@ -446,6 +445,13 @@
           </item>
          </layout>
         </item>
+        <item row="1" column="0">
+         <widget class="QLabel" name="label_baudrate">
+          <property name="text">
+           <string>Baudrate</string>
+          </property>
+         </widget>
+        </item>
         <item row="15" column="1">
          <widget class="QCheckBox" name="enableAETR">
           <property name="text">
@@ -458,7 +464,7 @@
       <item row="0" column="1">
        <layout class="QFormLayout" name="formLayout_2">
         <property name="labelAlignment">
-         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+         <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
         </property>
         <property name="horizontalSpacing">
          <number>6</number>
@@ -478,7 +484,7 @@
            <string>Start</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -497,7 +503,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string/>
@@ -531,7 +537,7 @@
            <string>Receiver No.</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -550,7 +556,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string/>
@@ -581,7 +587,7 @@
            <string>Polarity</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -600,7 +606,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
           <item>
            <property name="text">
@@ -630,7 +636,7 @@
            <string>Receiver 1</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -687,7 +693,7 @@
            <string>Receiver 2</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -723,7 +729,7 @@
            <string>Receiver 3</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -818,7 +824,7 @@
         <item row="9" column="0" colspan="2">
          <spacer name="horizontalSpacer_2">
           <property name="orientation">
-           <enum>Qt::Horizontal</enum>
+           <enum>Qt::Orientation::Horizontal</enum>
           </property>
           <property name="sizeHint" stdset="0">
            <size>
@@ -833,7 +839,7 @@
       <item row="0" column="2">
        <layout class="QFormLayout" name="formLayout_3">
         <property name="labelAlignment">
-         <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+         <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
         </property>
         <property name="horizontalSpacing">
          <number>6</number>
@@ -859,7 +865,7 @@
            <string>Channels</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -878,7 +884,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string/>
@@ -909,7 +915,7 @@
            <string>PPM delay</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -928,7 +934,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string> us</string>
@@ -959,7 +965,7 @@
            <string>PPM Frame Length</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -978,7 +984,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string> ms</string>
@@ -1012,7 +1018,7 @@
            <string>Antenna</string>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -1031,7 +1037,7 @@
            </size>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -1064,7 +1070,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
          </widget>
         </item>
@@ -1084,7 +1090,7 @@
            </sizepolicy>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
           <item>
            <property name="text">
@@ -1101,7 +1107,7 @@
         <item row="9" column="0" colspan="2">
          <spacer name="horizontalSpacer">
           <property name="orientation">
-           <enum>Qt::Horizontal</enum>
+           <enum>Qt::Orientation::Horizontal</enum>
           </property>
           <property name="sizeHint" stdset="0">
            <size>
@@ -1126,7 +1132,7 @@
            </size>
           </property>
           <property name="alignment">
-           <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           <set>Qt::AlignmentFlag::AlignRight|Qt::AlignmentFlag::AlignTrailing|Qt::AlignmentFlag::AlignVCenter</set>
           </property>
           <property name="suffix">
            <string> Hz</string>
@@ -1169,7 +1175,7 @@
            </sizepolicy>
           </property>
           <property name="sizeAdjustPolicy">
-           <enum>QComboBox::AdjustToContents</enum>
+           <enum>QComboBox::SizeAdjustPolicy::AdjustToContents</enum>
           </property>
          </widget>
         </item>
@@ -1200,7 +1206,7 @@ QGroupBox::title { subcontrol-origin: margin; subcontrol-position: top left; pad
          <property name="bottomMargin">
           <number>4</number>
          </property>
-         <item alignment="Qt::AlignRight">
+         <item alignment="Qt::AlignmentFlag::AlignRight">
           <widget class="QWidget" name="widgetValueType" native="true">
            <property name="autoFillBackground">
             <bool>true</bool>
diff --git a/radio/src/gui/colorlcd/module/crossfire_settings.cpp b/radio/src/gui/colorlcd/module/crossfire_settings.cpp
index 0c7110895..faf6be854 100644
--- a/radio/src/gui/colorlcd/module/crossfire_settings.cpp
+++ b/radio/src/gui/colorlcd/module/crossfire_settings.cpp
@@ -39,7 +39,7 @@ CrossfireSettings::CrossfireSettings(Window* parent, const FlexGridLayout& g,
     auto line = newLine(grid);
     new StaticText(line, rect_t{}, STR_BAUDRATE);
     new Choice(
-        line, rect_t{}, STR_CRSF_BAUDRATE, 0, CROSSFIRE_MAX_INTERNAL_BAUDRATE,
+        line, rect_t{}, STR_CRSF_BAUDRATE, 0, CROSSFIRE_MAX_EXTERNAL_BAUDRATE,
         [=]() -> int {
           return CROSSFIRE_STORE_TO_INDEX(md->crsf.telemetryBaudrate);
         },
diff --git a/radio/src/storage/storage_common.cpp b/radio/src/storage/storage_common.cpp
index 92cf584cc..a39d894de 100644
--- a/radio/src/storage/storage_common.cpp
+++ b/radio/src/storage/storage_common.cpp
@@ -211,6 +211,14 @@ if(g_model.rssiSource) {
 
   storageDirty(EE_MODEL);  
 }
+#if defined(STM32F4) && defined(CROSSFIRE)
+  // Limit ext. CRSF speed to 3.75Mbps due to CRC errors at higher speeds
+  if(isModuleCrossfire(EXTERNAL_MODULE) && g_model.moduleData[EXTERNAL_MODULE].crsf.telemetryBaudrate == 4) {
+	TRACE("Downgrading external ELRS module baudrate");
+    g_model.moduleData[EXTERNAL_MODULE].crsf.telemetryBaudrate = 3;
+    storageDirty(EE_MODEL);
+  }
+#endif
 
 #if defined(PXX2)
   bool changed = false;
diff --git a/radio/src/telemetry/crossfire.h b/radio/src/telemetry/crossfire.h
index 92d64d2b1..3653d8e83 100644
--- a/radio/src/telemetry/crossfire.h
+++ b/radio/src/telemetry/crossfire.h
@@ -130,6 +130,12 @@ const uint32_t CROSSFIRE_BAUDRATES[] = {
   5250000,
 };
 
+#if defined(STM32F4)
+#define CROSSFIRE_MAX_EXTERNAL_BAUDRATE     DIM(CROSSFIRE_BAUDRATES) - 2
+#else
+#define CROSSFIRE_MAX_EXTERNAL_BAUDRATE     DIM(CROSSFIRE_BAUDRATES) - 1
+#endif
+
 #if defined(RADIO_TPRO) || defined(RADIO_TPROV2) || defined(RADIO_T20)
 #define CROSSFIRE_MAX_INTERNAL_BAUDRATE     DIM(CROSSFIRE_BAUDRATES) - 3
 #else