diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32f47_mcuconf.h b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32f47_mcuconf.h
index 5bdcb72faa..384e48c331 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32f47_mcuconf.h
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32f47_mcuconf.h
@@ -580,3 +580,10 @@
 
 // limit ISR count per byte
 #define STM32_I2C_ISR_LIMIT                 6
+
+#if defined(STM32F7xx_MCUCONF)
+// disable DMA on I2C by default on F7
+#ifndef STM32_I2C_USE_DMA
+#define STM32_I2C_USE_DMA FALSE
+#endif
+#endif
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32h7_mcuconf.h b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32h7_mcuconf.h
index 9ab42b1260..f7884066f0 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/stm32h7_mcuconf.h
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/stm32h7_mcuconf.h
@@ -635,3 +635,7 @@
 #define STM32_SPI_SPI6_TX_BDMA_STREAM 5
 #define STM32_ADC_ADC3_BDMA_STREAM 7
 
+// disable DMA on I2C by default on H7
+#ifndef STM32_I2C_USE_DMA
+#define STM32_I2C_USE_DMA FALSE
+#endif
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 1edd3a6810..af75433bd4 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -151,7 +151,7 @@ def get_mcu_lib(mcu):
 
 def setup_mcu_type_defaults():
     '''setup defaults for given mcu type'''
-    global pincount, ports, portmap, vtypes, mcu_type
+    global pincount, ports, portmap, vtypes, mcu_type, dma_exclude_pattern
     lib = get_mcu_lib(mcu_type)
     if hasattr(lib, 'pincount'):
         pincount = lib.pincount
@@ -166,6 +166,9 @@ def setup_mcu_type_defaults():
         for pin in range(pincount[port]):
             portmap[port].append(generic_pin(port, pin, None, default_gpio[0], default_gpio[1:]))
 
+    if mcu_series.startswith("STM32H7") or mcu_series.startswith("STM32F7"):
+        # default DMA off on I2C for H7, we're much better off reducing DMA sharing
+        dma_exclude_pattern = ['I2C*']
 
 def get_alt_function(mcu, pin, function):
     '''return alternative function number for a pin'''