diff --git a/libraries/AP_HAL_ChibiOS/Util.cpp b/libraries/AP_HAL_ChibiOS/Util.cpp
index 03915504f9..2f801a2fb3 100644
--- a/libraries/AP_HAL_ChibiOS/Util.cpp
+++ b/libraries/AP_HAL_ChibiOS/Util.cpp
@@ -29,7 +29,7 @@
 #include <AP_Common/ExpandingString.h>
 #include "sdcard.h"
 #include "shared_dma.h"
-#if defined(HAL_PWM_ALARM) || HAL_DSHOT_ALARM || HAL_CANMANAGER_ENABLED || HAL_USE_PWM == TRUE
+#if defined(HAL_PWM_ALARM) || HAL_DSHOT_ALARM_ENABLED || HAL_CANMANAGER_ENABLED || HAL_USE_PWM == TRUE
 #include <AP_Notify/AP_Notify.h>
 #endif
 #if HAL_ENABLE_SAVE_PERSISTENT_PARAMS
@@ -171,7 +171,7 @@ bool Util::toneAlarm_init(uint8_t types)
 #endif
     _toneAlarm_types = types;
 
-#if HAL_USE_PWM != TRUE && !HAL_DSHOT_ALARM && !HAL_CANMANAGER_ENABLED
+#if HAL_USE_PWM != TRUE && !HAL_DSHOT_ALARM_ENABLED && !HAL_CANMANAGER_ENABLED
     // Nothing to do
     return false;
 #else
@@ -209,7 +209,7 @@ void Util::toneAlarm_set_buzzer_tone(float frequency, float volume, uint32_t dur
         }
     }
 #endif // HAL_USE_PWM
-#if HAL_DSHOT_ALARM
+#if HAL_DSHOT_ALARM_ENABLED
     // don't play the motors while flying
     if (!(_toneAlarm_types & AP_Notify::Notify_Buzz_DShot) || get_soft_armed() || hal.rcout->get_dshot_esc_type() != RCOutput::DSHOT_ESC_BLHELI) {
         return;
@@ -228,7 +228,7 @@ void Util::toneAlarm_set_buzzer_tone(float frequency, float volume, uint32_t dur
     } else {  // G+
         hal.rcout->send_dshot_command(RCOutput::DSHOT_BEEP5, RCOutput::ALL_CHANNELS, duration_ms);
     }
-#endif // HAL_DSHOT_ALARM
+#endif // HAL_DSHOT_ALARM_ENABLED
 }
 
 /*
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 98c0d5383b..bba02f8315 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -2345,6 +2345,9 @@ def write_hwdef_header(outfilename):
     write_AIRSPEED_config(f)
     write_board_validate_macro(f)
     add_apperiph_defaults(f)
+    add_bootloader_defaults(f)
+    add_iomcu_firmware_defaults(f)
+    add_normal_firmware_defaults(f)
     write_check_firmware(f)
 
     write_peripheral_enable(f)
@@ -2784,6 +2787,8 @@ def add_apperiph_defaults(f):
 
     print("Setting up as AP_Periph")
     f.write('''
+// AP_Periph defaults
+
 #ifndef HAL_SCHEDULER_ENABLED
 #define HAL_SCHEDULER_ENABLED 0
 #endif
@@ -2913,6 +2918,51 @@ def add_apperiph_defaults(f):
 
 ''')
 
+def add_bootloader_defaults(f):
+    '''add default defines for peripherals'''
+    if not args.bootloader:
+        return
+
+    print("Setting up as Bootloader")
+    f.write('''
+// AP_Bootloader defaults
+
+#define HAL_DSHOT_ALARM_ENABLED 0
+''')
+
+def add_iomcu_firmware_defaults(f):
+    '''add default defines IO firmwares'''
+    if env_vars.get('IOMCU_FW', 0) == 0:
+        # not IOMCU firmware
+        return
+
+    print("Setting up as IO firmware")
+    f.write('''
+// IOMCU Firmware defaults
+
+#define HAL_DSHOT_ALARM_ENABLED 0
+''')
+
+def add_normal_firmware_defaults(f):
+    '''add default defines to builds with are not bootloader, periph or IOMCU'''
+    if env_vars.get('IOMCU_FW', 0) != 0:
+        # IOMCU firmware
+        return
+    if env_vars.get('AP_PERIPH', 0) != 0:
+        # Periph firmware
+        return
+    if args.bootloader:
+        # guess
+        return
+
+    print("Setting up as normal firmware")
+    f.write('''
+// firmware defaults
+
+#ifndef HAL_DSHOT_ALARM_ENABLED
+#define HAL_DSHOT_ALARM_ENABLED (HAL_PWM_COUNT>0)
+#endif
+''')
 
 # process input file
 for fname in args.hwdef: