sm_host: DTE DTR

CMakeLists.txt

@@ -6,4 +6,5 @@
 
 zephyr_include_directories(include)
 
+add_subdirectory(drivers)
 add_subdirectory(lib)

Kconfig

@@ -5,4 +5,5 @@
 # as the module Kconfig entry point (see zephyr/module.yml). You can browse
 # module options by going to Zephyr -> Modules in Kconfig.
 
+rsource "drivers/Kconfig"
 rsource "lib/Kconfig"

app/boards/nrf9151dk_nrf9151_ns.conf

@@ -9,7 +9,7 @@
 # set here will take precedence if they are present in both files.
 
 # When working with PC terminal, unmask the following config.
-CONFIG_SM_POWER_PIN=8
+CONFIG_SM_POWER_PIN=-1
 CONFIG_SM_INDICATE_PIN=0
 
 # When working with external MCU, unmask the following config.

app/boards/nrf9151dk_nrf9151_ns.overlay

@@ -6,54 +6,33 @@
 
  / {
 	chosen {
-		ncs,sm-uart = &uart0;
+		ncs,sm-uart = &dtr_uart0;
 	};
 };
 
+/* DTR with DK */
 &uart0 {
 	status = "okay";
 	hw-flow-control;
-};
 
-&uart2 {
-	compatible = "nordic,nrf-uarte";
-	current-speed = <115200>;
-	status = "disabled";
-	hw-flow-control;
+	dtr_uart0: dtr-uart {
+		compatible = "nordic,dtr-uart";
+		dtr-gpios = <&gpio0 8 (GPIO_PULL_UP | GPIO_ACTIVE_HIGH)>;
+		ri-gpios = <&gpio0 0 GPIO_ACTIVE_LOW>;
+		status = "okay";
+	};
+};
 
-	pinctrl-0 = <&uart2_default_alt>;
-	pinctrl-1 = <&uart2_sleep_alt>;
-	pinctrl-names = "default", "sleep";
+&gpio0 {
+	status = "okay";
+	/* Use PORT event for DTR (8) and RI (0) pins to save power */
+	sense-edge-mask = <0x00000101>;
 };
 
 &i2c2 {
 	status = "disabled";
 };
 
-&pinctrl {
-	uart2_default_alt: uart2_default_alt {
-		group1 {
-			psels = <NRF_PSEL(UART_RX, 0, 11)>;
-			bias-pull-up;
-		};
-		group2 {
-			psels = <NRF_PSEL(UART_TX, 0, 10)>,
-				<NRF_PSEL(UART_RTS, 0, 12)>,
-				<NRF_PSEL(UART_CTS, 0, 13)>;
-		};
-	};
-
-	uart2_sleep_alt: uart2_sleep_alt {
-		group1 {
-			psels = <NRF_PSEL(UART_TX, 0, 10)>,
-				<NRF_PSEL(UART_RX, 0, 11)>,
-				<NRF_PSEL(UART_RTS, 0, 12)>,
-				<NRF_PSEL(UART_CTS, 0, 13)>;
-			low-power-enable;
-		};
-	};
-};
-
 /* Enable external flash */
 &gd25wb256 {
 	status = "okay";

app/overlay-cmux.conf

@@ -11,18 +11,6 @@ CONFIG_SM_SKIP_READY_MSG=y
 CONFIG_MODEM_MODULES=y
 CONFIG_MODEM_CMUX=y
 
-# Enable Serial Modem UART backend
-CONFIG_MODEM_BACKEND_UART=n
-CONFIG_MODEM_BACKEND_UART_ASYNC=n
-CONFIG_MODEM_BACKEND_UART_SLM=y
-CONFIG_MODEM_BACKEND_UART_SLM_TRANSMIT_TIMEOUT_MS=1000
-
-# These buffers are unused after AT#CMUX is enabled
-# so use minimal buffer size
-CONFIG_SM_UART_RX_BUF_COUNT=2
-CONFIG_SM_UART_RX_BUF_SIZE=128
-CONFIG_SM_UART_TX_BUF_SIZE=128
-
 # debug options
 #CONFIG_MODEM_CMUX_LOG_LEVEL_DBG=y
 #CONFIG_MODEM_MODULES_LOG_LEVEL_DBG=y

app/overlay-external-mcu-nrf91x1.conf

@@ -0,0 +1,9 @@
+# Segger RTT
+CONFIG_USE_SEGGER_RTT=n
+# Where console messages (printk) are output.
+# By itself, SM does not output any.
+CONFIG_RTT_CONSOLE=n
+CONFIG_UART_CONSOLE=y
+# Where logs are output.
+CONFIG_LOG_BACKEND_RTT=n
+CONFIG_LOG_BACKEND_UART=y

app/overlay-external-mcu-nrf91x1.overlay

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		ncs,sm-uart = &dtr_uart2;
+	};
+};
+
+/* For logging. TODO: Disable. */
+// &uart0 {
+// 	status = "okay";
+// 	hw-flow-control;
+// };
+
+&uart0 {
+	status = "disabled";
+};
+
+&dtr_uart0 {
+	status = "disabled";
+};
+
+
+&gpio0 {
+	status = "okay";
+	/* Use PORT event for DTR (31) and RI (30) pins to save power */
+	sense-edge-mask = <0xC0000000>;
+};
+
+/* DTR with external MCU */
+&uart2 {
+	compatible = "nordic,nrf-uarte";
+	current-speed = <115200>;
+	hw-flow-control;
+	status = "okay";
+
+	dtr_uart2: dtr-uart {
+		compatible = "nordic,dtr-uart";
+		dtr-gpios = <&gpio0 31 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
+		ri-gpios = <&gpio0 30 GPIO_ACTIVE_LOW>;
+		status = "okay";
+	};
+	pinctrl-0 = <&uart2_default_alt>;
+	pinctrl-1 = <&uart2_sleep_alt>;
+	pinctrl-names = "default", "sleep";
+};
+
+
+&pinctrl {
+	uart2_default_alt: uart2_default_alt {
+		group1 {
+			psels = <NRF_PSEL(UART_RX, 0, 11)>;
+			bias-pull-up;
+		};
+		group2 {
+			psels = <NRF_PSEL(UART_TX, 0, 10)>,
+				<NRF_PSEL(UART_RTS, 0, 12)>,
+				<NRF_PSEL(UART_CTS, 0, 13)>;
+		};
+	};
+
+	uart2_sleep_alt: uart2_sleep_alt {
+		group1 {
+			psels = <NRF_PSEL(UART_TX, 0, 10)>,
+				<NRF_PSEL(UART_RX, 0, 11)>,
+				<NRF_PSEL(UART_RTS, 0, 12)>,
+				<NRF_PSEL(UART_CTS, 0, 13)>;
+			low-power-enable;
+		};
+	};
+};

app/overlay-ppp-cmux-linux.conf

@@ -11,25 +11,12 @@ CONFIG_SM_CR_TERMINATION=y
 
 CONFIG_MODEM_CMUX_MTU=127
 CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE=536
-CONFIG_SM_CMUX_UART_BUFFER_SIZE=600
 
-# Enable Serial Modem UART backend
-CONFIG_MODEM_BACKEND_UART=n
-CONFIG_MODEM_BACKEND_UART_ASYNC=n
-CONFIG_MODEM_BACKEND_UART_SLM=y
-
-# For sending full 600 bytes at 115200 baudrate
-# 600 * 10 / 115200 = 52.1 ms
-CONFIG_MODEM_BACKEND_UART_SLM_TRANSMIT_TIMEOUT_MS=53
-# Assume at least baudrate 115200 for UART
-# so CMUX frame can be received in 12 ms (134*10/115200)
-CONFIG_MODEM_BACKEND_UART_SLM_RECEIVE_IDLE_TIMEOUT_MS=12
-
-# These buffers are unused after AT#CMUX is enabled
-# so use minimal buffer size
-CONFIG_SM_UART_RX_BUF_COUNT=2
-CONFIG_SM_UART_RX_BUF_SIZE=128
-CONFIG_SM_UART_TX_BUF_SIZE=128
+# With CMUX, the UART buffers should be at least the size of the
+# CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE
+CONFIG_SM_UART_RX_BUF_COUNT=3
+CONFIG_SM_UART_RX_BUF_SIZE=256
+CONFIG_SM_UART_TX_BUF_SIZE=768
 
 # When using PPP, disable commands of IP-based protocols to save flash space.
 CONFIG_SM_FTPC=n

app/overlay-ppp-without-cmux.conf

@@ -0,0 +1,8 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+# Enable modem UART backend
+CONFIG_MODEM_BACKEND_UART=y
+CONFIG_MODEM_BACKEND_UART_ASYNC=y

app/overlay-ppp.conf

@@ -24,12 +24,6 @@ CONFIG_NET_L2_PPP=y
 CONFIG_MODEM_MODULES=y
 CONFIG_MODEM_PPP=y
 
-# Enable Serial Modem UART backend
-CONFIG_MODEM_BACKEND_UART=n
-CONFIG_MODEM_BACKEND_UART_ASYNC=n
-CONFIG_MODEM_BACKEND_UART_SLM=y
-CONFIG_MODEM_BACKEND_UART_SLM_TRANSMIT_TIMEOUT_MS=1000
-
 # L2 protocol
 CONFIG_NET_L2_PPP_MGMT=y
 CONFIG_NET_L2_PPP_OPTION_MRU=y

app/overlay-zephyr-modem-nrf9160dk-nrf52840.conf

@@ -5,4 +5,30 @@
 #
 
 # nRF52 <=> nRF91 interface pin 4 (see https://docs.nordicsemi.com/bundle/ug_nrf91_dk/page/UG/nrf91_DK/board_controller.html)
-CONFIG_SM_POWER_PIN=22
+CONFIG_SLM_POWER_PIN=-1
+
+CONFIG_USE_SEGGER_RTT=n
+# Where console messages (printk) are output.
+# By itself, SLM does not output any.
+CONFIG_RTT_CONSOLE=n
+CONFIG_UART_CONSOLE=y
+# Where SLM logs are output.
+CONFIG_LOG_BACKEND_RTT=n
+CONFIG_LOG_BACKEND_UART=y
+
+CONFIG_SHELL=y
+CONFIG_GPIO=y
+CONFIG_GPIO_SHELL=y
+CONFIG_PM_DEVICE_SHELL=y
+
+CONFIG_UART_1_INTERRUPT_DRIVEN=n
+CONFIG_UART_1_ASYNC=y
+CONFIG_UART_USE_RUNTIME_CONFIGURE=y
+CONFIG_UART_ASYNC_API=y
+
+CONFIG_SLM_SMS=n
+CONFIG_SLM_GNSS=n
+CONFIG_SLM_NRF_CLOUD=n
+CONFIG_SLM_GPIO=n
+
+CONFIG_SIZE_OPTIMIZATIONS_AGGRESSIVE=y

app/overlay-zephyr-modem-nrf9160dk-nrf52840.overlay

@@ -8,11 +8,18 @@
 
 / {
 	chosen {
-		ncs,sm-uart = &uart1;
+		ncs,sm-uart = &dtr_uart;
 	};
 };
 
 &uart1 {
         current-speed = <115200>;
         hw-flow-control;
+	status = "okay";
+	dtr_uart: dtr-uart {
+		compatible = "nordic,dtr-uart";
+		dtr-gpios = <&interface_to_nrf52840 4 (GPIO_PULL_UP | GPIO_ACTIVE_LOW)>;
+		ri-gpios = <&interface_to_nrf52840 5 (GPIO_ACTIVE_LOW)>;
+		status = "okay";
+	};
 };

app/prj.conf

@@ -29,6 +29,10 @@ CONFIG_LOG_BACKEND_UART=n
 # errors if Serial Modem does not start properly.
 CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=2048
 
+# DTR UART
+CONFIG_DTR_UART=y
+CONFIG_DTR_UART_LOG_LEVEL_DBG=y
+
 # Network
 CONFIG_NETWORKING=y
 CONFIG_NET_SOCKETS=y
@@ -133,6 +137,7 @@ CONFIG_SM_EXTERNAL_XTAL=n
 #CONFIG_SM_LOG_LEVEL_DBG=y
 #CONFIG_LOG_PRINTK=n
 #CONFIG_LOG_MODE_IMMEDIATE=y
+CONFIG_DEBUG_OPTIMIZATIONS=y
 
 # For using external GNSS antenna
 #CONFIG_MODEM_ANTENNA=y

app/sample.yaml

@@ -85,6 +85,7 @@ tests:
     build_only: true
     extra_args:
       - EXTRA_CONF_FILE="overlay-ppp.conf"
+      - EXTRA_CONF_FILE="overlay-ppp-without-cmux.conf"
       - EXTRA_DTC_OVERLAY_FILE="overlay-ppp-without-cmux.overlay"
     platform_allow:
       - nrf9160dk/nrf9160/ns
@@ -104,6 +105,7 @@ tests:
     build_only: true
     extra_args:
       - EXTRA_CONF_FILE="overlay-ppp.conf"
+      - EXTRA_CONF_FILE="overlay-ppp-without-cmux.conf"
       - EXTRA_DTC_OVERLAY_FILE="overlay-ppp-without-cmux.overlay"
     extra_configs:
       - CONFIG_SM_POWER_PIN=31