diff --git a/libraries/AP_HAL_ChibiOS/hwdef/iomcu/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/iomcu/hwdef.dat
index 2c5c90bab3..c595075e0d 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/iomcu/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/iomcu/hwdef.dat
@@ -29,6 +29,7 @@ define HAL_USE_UART TRUE
 PA2 USART2_TX USART2
 PA3 USART2_RX USART2
 
+define STM32_UART_USE_USART1 FALSE
 define STM32_UART_USE_USART2 TRUE
 define STM32_UART_USE_USART3 FALSE
 
@@ -37,6 +38,8 @@ define HAL_USE_SERIAL TRUE
 PB4 SBUS_OUT_EN OUTPUT LOW GPIO(1)
 PB10 USART3_TX USART3
 PB11 USART3_RX USART3
+
+define STM32_SERIAL_USE_USART1 TRUE
 define STM32_SERIAL_USE_USART2 FALSE
 define STM32_SERIAL_USE_USART3 TRUE
 
@@ -62,6 +65,14 @@ PB14 HEATER OUTPUT GPIO(0)
 PB5 SAFETY_INPUT INPUT PULLDOWN
 PB13 SAFETY_LED OUTPUT HIGH
 
+# UART for DSM input
+# TX side is for IO debug, and is unused
+PA9  USART1_TX USART1
+PA10 USART1_RX USART1
+
+PC13 SPEKTRUM_PWR_EN OUTPUT LOW
+define HAL_GPIO_PIN_SPEKTRUM_OUT PAL_LINE(GPIOA,10U)
+
 PA8 INPUT PULLUP # RC Input PPM
 
 # analog inputs
@@ -91,8 +102,6 @@ define HAL_INS_DEFAULT HAL_INS_NONE
 define HAL_BARO_DEFAULT HAL_BARO_NONE
 define HAL_NO_GPIO_IRQ
 define CH_CFG_ST_TIMEDELTA 0
-define TIMER_THD_WA_SIZE 256
-define RCIN_THD_WA_SIZE 768
 #define CH_CFG_USE_DYNAMIC FALSE
 define SERIAL_BUFFERS_SIZE 32
 define HAL_USE_EMPTY_IO TRUE