diff --git a/boards/mro/x21-777/nuttx-config/nsh/defconfig b/boards/mro/x21-777/nuttx-config/nsh/defconfig
index 65072334e0..1ddbbe7600 100644
--- a/boards/mro/x21-777/nuttx-config/nsh/defconfig
+++ b/boards/mro/x21-777/nuttx-config/nsh/defconfig
@@ -198,9 +198,9 @@ CONFIG_SYSTEM_CDCACM=y
 CONFIG_SYSTEM_NSH=y
 CONFIG_TASK_NAME_SIZE=24
 CONFIG_UART4_BAUD=57600
-CONFIG_UART4_RXBUFSIZE=600
-CONFIG_UART4_RXDMA=y
-CONFIG_UART4_TXBUFSIZE=1500
+CONFIG_UART4_RXBUFSIZE=1200
+CONFIG_UART4_RXDMA=n
+CONFIG_UART4_TXBUFSIZE=1200
 CONFIG_UART7_BAUD=57600
 CONFIG_UART7_RXBUFSIZE=600
 CONFIG_UART7_SERIAL_CONSOLE=y
@@ -225,10 +225,10 @@ CONFIG_USART3_RXBUFSIZE=600
 CONFIG_USART3_RXDMA=y
 CONFIG_USART3_TXBUFSIZE=3000
 CONFIG_USART6_BAUD=57600
-CONFIG_USART6_RXBUFSIZE=600
-CONFIG_USART6_RXDMA=y
-CONFIG_USART6_TXBUFSIZE=1500
-CONFIG_USART6_TXDMA=y
+CONFIG_USART6_RXBUFSIZE=1200
+CONFIG_USART6_RXDMA=n
+CONFIG_USART6_TXBUFSIZE=1200
+CONFIG_USART6_TXDMA=n
 CONFIG_USBDEV=y
 CONFIG_USBDEV_BUSPOWERED=y
 CONFIG_USBDEV_MAXPOWER=500