diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F745xx.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F745xx.py
index 1a5496147c..9150b1bfd3 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F745xx.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F745xx.py
@@ -21,7 +21,13 @@ mcu = {
     'RAM_MAP' : [
         (0x20010000, 256, 0), # main memory, not DMA safe
         (0x20000000,  64, 1), # DTCM memory, DMA safe
-    ]
+    ],
+
+    # this board has M7 instructions, but single precision only FPU
+    # we build as m4 as it makes for a smaller build, and given the 1M
+    # flash limit we care more about size
+    'CORTEX'    : 'cortex-m4',
+    'CPU_FLAGS' : '-mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard'
 }
 
 DMA_Map = {
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F767xx.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F767xx.py
index 68e6ea4bda..a881c629cc 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F767xx.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F767xx.py
@@ -38,7 +38,11 @@ mcu = {
         # split DTCM in two to allow for fast checking of IS_DMA_SAFE in bouncebuffer code
         (0x20000000,  64, 1), # DTCM, DMA safe
         (0x20010000,  64, 2), # DTCM, 2nd half, used as fast memory. This lowers memory contention in the EKF code
-    ]
+    ],
+
+    # this MCU has M7 instructions and hardware double precision
+    'CORTEX'    : 'cortex-m7',
+    'CPU_FLAGS' : '-mcpu=cortex-m7 -mfpu=fpv5-d16 -mfloat-abi=hard',
 }
 
 DMA_Map = {
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F777xx.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F777xx.py
index 8a760476c5..f0f905af63 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F777xx.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F777xx.py
@@ -35,7 +35,11 @@ mcu = {
     'RAM_MAP' : [
         (0x20020000, 384, 0), # SRAM1/SRAM2
         (0x20000000, 128, 1), # DTCM, DMA
-    ]
+    ],
+
+    # this MCU has M7 instructions and hardware double precision
+    'CORTEX'    : 'cortex-m7',
+    'CPU_FLAGS' : '-mcpu=cortex-m7 -mfpu=fpv5-d16 -mfloat-abi=hard',
 }
 
 DMA_Map = {
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32H743xx.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32H743xx.py
index 23a329aff7..fafe084eed 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32H743xx.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32H743xx.py
@@ -24,7 +24,11 @@ mcu = {
         (0x38000000,  64, 1), # SRAM4. This supports both DMA and BDMA ops
         (0x24000000, 512, 4), # AXI SRAM. Use this for SDMMC IDMA ops
         (0x00000400,  63, 2), # ITCM (first 1k removed, to keep address 0 unused)
-    ]
+    ],
+
+    # this MCU has M7 instructions and hardware double precision
+    'CORTEX'    : 'cortex-m7',
+    'CPU_FLAGS' : '-mcpu=cortex-m7 -mfpu=fpv5-d16 -mfloat-abi=hard',
 }
 
 pincount = {
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 4355d82cdc..cce6d9b1e2 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -705,17 +705,26 @@ def write_mcu_config(f):
     lib = get_mcu_lib(mcu_type)
     build_info = lib.build
 
-    if mcu_series.startswith("STM32F1"):
+    if get_mcu_config('CPU_FLAGS') and get_mcu_config('CORTEX'):
+        # CPU flags specified in mcu file
+        cortex = get_mcu_config('CORTEX')
+        env_vars['CPU_FLAGS'] = get_mcu_config('CPU_FLAGS').split()
+        build_info['MCU'] = cortex
+        print("MCU Flags: %s %s" % (cortex, env_vars['CPU_FLAGS']))
+    elif mcu_series.startswith("STM32F1"):
         cortex = "cortex-m3"
         env_vars['CPU_FLAGS'] = ["-mcpu=%s" % cortex]
         build_info['MCU'] = cortex
     else:
+        # default to F4
         cortex = "cortex-m4"
         env_vars['CPU_FLAGS'] = ["-mcpu=%s" % cortex, "-mfpu=fpv4-sp-d16", "-mfloat-abi=hard"]
         build_info['MCU'] = cortex
-        if not args.bootloader:
-            env_vars['CPU_FLAGS'].append('-u_printf_float')
-            build_info['ENV_UDEFS'] = "-DCHPRINTF_USE_FLOAT=1"
+
+    if not mcu_series.startswith("STM32F1") and not args.bootloader:
+        env_vars['CPU_FLAGS'].append('-u_printf_float')
+        build_info['ENV_UDEFS'] = "-DCHPRINTF_USE_FLOAT=1"
+
     # setup build variables
     for v in build_info.keys():
         build_flags.append('%s=%s' % (v, build_info[v]))