modem_cellular: Add support for the simcom a76xx modem

drivers/modem/Kconfig.cellular

@@ -14,7 +14,7 @@ config MODEM_CELLULAR
 	select NET_L2_PPP_OPTION_MRU
 	select NET_L2_PPP_PAP
 	select NET_L2_PPP_MGMT
-	depends on (DT_HAS_QUECTEL_BG95_ENABLED || \
+	depends on (DT_HAS_QUECTEL_BG95_ENABLED || DT_HAS_SIMCOM_A76XX_ENABLED || \
 		    DT_HAS_SIMCOM_SIM7080_ENABLED || DT_HAS_U_BLOX_SARA_R4_ENABLED || \
 		    DT_HAS_U_BLOX_SARA_R5_ENABLED || DT_HAS_SWIR_HL7800_ENABLED || \
 		    DT_HAS_TELIT_ME910G1_ENABLED || DT_HAS_TELIT_ME310G1_ENABLED || \
@@ -63,4 +63,8 @@ config MODEM_CELLULAR_NEW_BAUDRATE_DELAY
 	default 100 if DT_HAS_U_BLOX_LARA_R6_ENABLED
 	default 300
 
+config MODEM_CELLULAR_POWER_ON_GNSS
+	bool "Power on the modem's GNSS module"
+	depends on DT_HAS_SIMCOM_A76XX_ENABLED
+	default n
 endif

drivers/modem/modem_cellular.c

@@ -525,7 +525,9 @@ MODEM_CHAT_MATCHES_DEFINE(dial_abort_matches,
 			  MODEM_CHAT_MATCH("NO CARRIER", "", NULL),
 			  MODEM_CHAT_MATCH("NO DIALTONE", "", NULL));
 
-#if DT_HAS_COMPAT_STATUS_OKAY(swir_hl7800) || DT_HAS_COMPAT_STATUS_OKAY(sqn_gm02s)
+#if DT_HAS_COMPAT_STATUS_OKAY(swir_hl7800) || \
+	DT_HAS_COMPAT_STATUS_OKAY(sqn_gm02s) || \
+	DT_HAS_COMPAT_STATUS_OKAY(simcom_a76xx)
 MODEM_CHAT_MATCH_DEFINE(connect_match, "CONNECT", "", NULL);
 #endif
 
@@ -616,6 +618,8 @@ static int modem_cellular_on_idle_state_enter(struct modem_cellular_data *data)
 	}
 
 	modem_cellular_notify_user_pipes_disconnected(data);
+	net_if_carrier_off(modem_ppp_get_iface(data->ppp));
+	net_if_dormant_off(modem_ppp_get_iface(data->ppp));
 	modem_chat_release(&data->chat);
 	modem_ppp_release(data->ppp);
 	modem_cmux_release(&data->cmux);
@@ -2064,6 +2068,66 @@ MODEM_CHAT_SCRIPT_DEFINE(simcom_sim7080_periodic_chat_script,
 			 modem_cellular_chat_callback_handler, 4);
 #endif
 
+#if DT_HAS_COMPAT_STATUS_OKAY(simcom_a76xx)
+MODEM_CHAT_SCRIPT_CMDS_DEFINE(simcom_a76xx_init_chat_script_cmds,
+			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT", 100),
+			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT", 100),
+			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT", 100),
+			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT", 100),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("ATE0", ok_match),
+			      #if CONFIG_MODEM_CELLULAR_POWER_ON_GNSS
+			      /* Power on the GNSS module.
+			       * We need to do this early, otherwise it does not work when
+			       * doing it later (e.g. from a user pipe).
+			       */
+			      MODEM_CHAT_SCRIPT_CMD_RESP_MULT("AT+CGNSSPWR=1", allow_match),
+			      #endif
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CFUN=4", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CMEE=1", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CREG=1", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGREG=1", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CEREG=1", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CREG?", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CEREG?", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGREG?", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGSN", imei_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGMM", cgmm_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT+CMUX=0,0,5,127", 300));
+
+MODEM_CHAT_SCRIPT_DEFINE(simcom_a76xx_init_chat_script, simcom_a76xx_init_chat_script_cmds,
+			 abort_matches, modem_cellular_chat_callback_handler, 10);
+
+MODEM_CHAT_SCRIPT_CMDS_DEFINE(simcom_a76xx_dial_chat_script_cmds,
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGDCONT=1,\"IP\","
+							 "\""CONFIG_MODEM_CELLULAR_APN"\"",
+							 ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP_MULT("AT+CGACT=0,1", allow_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CFUN=1", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("ATD*99***1#", connect_match),);
+
+MODEM_CHAT_SCRIPT_DEFINE(simcom_a76xx_dial_chat_script, simcom_a76xx_dial_chat_script_cmds,
+			 dial_abort_matches, modem_cellular_chat_callback_handler, 10);
+
+MODEM_CHAT_SCRIPT_CMDS_DEFINE(simcom_a76xx_periodic_chat_script_cmds,
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CREG?", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CEREG?", ok_match),
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CGREG?", ok_match));
+
+MODEM_CHAT_SCRIPT_DEFINE(simcom_a76xx_periodic_chat_script,
+			 simcom_a76xx_periodic_chat_script_cmds, abort_matches,
+			 modem_cellular_chat_callback_handler, 4);
+
+MODEM_CHAT_SCRIPT_CMDS_DEFINE(simcom_a76xx_shutdown_chat_script_cmds,
+			      MODEM_CHAT_SCRIPT_CMD_RESP("AT+CPOF", ok_match));
+
+MODEM_CHAT_SCRIPT_DEFINE(simcom_a76xx_shutdown_chat_script,
+			 simcom_a76xx_shutdown_chat_script_cmds, abort_matches,
+			 modem_cellular_chat_callback_handler, 15);
+
+#endif
+
 #if DT_HAS_COMPAT_STATUS_OKAY(u_blox_sara_r4)
 MODEM_CHAT_SCRIPT_CMDS_DEFINE(u_blox_sara_r4_init_chat_script_cmds,
 			      MODEM_CHAT_SCRIPT_CMD_RESP_NONE("AT", 100),
@@ -2567,6 +2631,26 @@ MODEM_CHAT_SCRIPT_DEFINE(sqn_gm02s_periodic_chat_script,
 				       &simcom_sim7080_dial_chat_script,                           \
 				       &simcom_sim7080_periodic_chat_script, NULL)
 
+#define MODEM_CELLULAR_DEVICE_SIMCOM_A76XX(inst)                                                   \
+	MODEM_PPP_DEFINE(MODEM_CELLULAR_INST_NAME(ppp, inst), NULL, 98, 1500, 64);                 \
+                                                                                                   \
+	static struct modem_cellular_data MODEM_CELLULAR_INST_NAME(data, inst) = {                 \
+		.chat_delimiter = "\r",                                                            \
+		.chat_filter = "\n",                                                               \
+		.ppp = &MODEM_CELLULAR_INST_NAME(ppp, inst),                                       \
+	};                                                                                         \
+                                                                                                   \
+	MODEM_CELLULAR_DEFINE_AND_INIT_USER_PIPES(inst,                                            \
+						  (user_pipe_0, 3),                                \
+						  (user_pipe_1, 4))                                \
+                                                                                                   \
+	MODEM_CELLULAR_DEFINE_INSTANCE(inst, 500, 100, 20000, 5000, false,                         \
+				       NULL,                                                       \
+				       &simcom_a76xx_init_chat_script,                             \
+				       &simcom_a76xx_dial_chat_script,                             \
+				       &simcom_a76xx_periodic_chat_script,                         \
+				       &simcom_a76xx_shutdown_chat_script)
+
 #define MODEM_CELLULAR_DEVICE_U_BLOX_SARA_R4(inst)                                                 \
 	MODEM_PPP_DEFINE(MODEM_CELLULAR_INST_NAME(ppp, inst), NULL, 98, 1500, 64);                 \
                                                                                                    \
@@ -2730,6 +2814,10 @@ DT_INST_FOREACH_STATUS_OKAY(MODEM_CELLULAR_DEVICE_QUECTEL_EG25_G)
 DT_INST_FOREACH_STATUS_OKAY(MODEM_CELLULAR_DEVICE_SIMCOM_SIM7080)
 #undef DT_DRV_COMPAT
 
+#define DT_DRV_COMPAT simcom_a76xx
+DT_INST_FOREACH_STATUS_OKAY(MODEM_CELLULAR_DEVICE_SIMCOM_A76XX)
+#undef DT_DRV_COMPAT
+
 #define DT_DRV_COMPAT u_blox_sara_r4
 DT_INST_FOREACH_STATUS_OKAY(MODEM_CELLULAR_DEVICE_U_BLOX_SARA_R4)
 #undef DT_DRV_COMPAT

dts/bindings/modem/simcom,a76xx.yaml

@@ -0,0 +1,13 @@
+# Copyright (C) 2021 metraTec GmbH
+# SPDX-License-Identifier: Apache-2.0
+
+description: Simcom A76XX modem
+
+compatible: "simcom,a76xx"
+
+include: uart-device.yaml
+
+properties:
+  mdm-power-gpios:
+    type: phandle-array
+    required: true

samples/net/cellular_modem/Kconfig

@@ -0,0 +1,12 @@
+# Copyright (c) 2025 Olivier Lalonde
+# SPDX-License-Identifier: Apache-2.0
+
+# Configuration options for cellular modem sample
+
+mainmenu "Cellular modem sample application"
+
+config SAMPLE_CELLULAR_MODEM_ENDPOINT_HOSTNAME
+	string "Endpoint hostname"
+	default "test-endpoint.com"
+
+source "Kconfig.zephyr"

samples/net/cellular_modem/README.rst

@@ -55,3 +55,11 @@ Next, the UART API must be specified using ``CONFIG_UART_INTERRUPT_DRIVEN=y`` or
 ``CONFIG_UART_ASYNC_API=y``. The driver doesn't support UART polling.
 
 Lastly, the APN must be configured using ``CONFIG_MODEM_CELLULAR_APN=""``.
+
+Server setup
+************
+
+.. code-block:: shell
+        git clone --depth=1 https://github.com/zephyrproject-rtos/zephyr.git
+        cd zephyr/samples/net/cellular_modem/server
+        python te.py

samples/net/cellular_modem/boards/nrf52840dk_nrf52840.conf

@@ -0,0 +1,3 @@
+# Otherwise we run into DLCI buffer overruns (maybe due to lack of UART hardware flow control?)
+CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE=1507
+CONFIG_NET_IPV6=n

samples/net/cellular_modem/boards/nrf52840dk_nrf52840.overlay

@@ -0,0 +1,27 @@
+/ {
+	aliases {
+		modem = &modem;
+	};
+};
+
+/* Tested with Simcom A7672SA module connected via UART
+ * TX: P1.2
+ * RX: P1.1
+ * PWRKEY: P0.02
+ */
+&uart1 {
+	compatible = "nordic,nrf-uarte";
+	status = "okay";
+	current-speed = <115200>;
+	/* The module I tested with doesn't expose RCS/CTS pins
+	 * hw-flow-control;
+	 */
+
+	pinctrl-0 = <&uart1_default>;
+
+	modem: modem {
+		compatible = "simcom,a76xx";
+		status = "okay";
+		mdm-power-gpios = <&gpio0 2 (GPIO_ACTIVE_HIGH)>;
+	};
+};

samples/net/cellular_modem/src/main.c

@@ -15,7 +15,7 @@
 
 #include <zephyr/drivers/cellular.h>
 
-#define SAMPLE_TEST_ENDPOINT_HOSTNAME		("test-endpoint.com")
+#define SAMPLE_TEST_ENDPOINT_HOSTNAME		CONFIG_SAMPLE_CELLULAR_MODEM_ENDPOINT_HOSTNAME
 #define SAMPLE_TEST_ENDPOINT_UDP_ECHO_PORT	(7780)
 #define SAMPLE_TEST_ENDPOINT_UDP_RECEIVE_PORT	(7781)
 #define SAMPLE_TEST_PACKET_SIZE			(1024)

subsys/modem/Kconfig

@@ -35,7 +35,7 @@ config MODEM_CMUX_DEFAULT_MTU_127
 		      DT_HAS_SIMCOM_SIM7080_ENABLED || DT_HAS_U_BLOX_SARA_R4_ENABLED || \
 		      DT_HAS_U_BLOX_SARA_R5_ENABLED || DT_HAS_SWIR_HL7800_ENABLED || \
 		      DT_HAS_TELIT_ME910G1_ENABLED || DT_HAS_TELIT_ME310G1_ENABLED || \
-		      DT_HAS_SQN_GM02S_ENABLED)
+		      DT_HAS_SQN_GM02S_ENABLED || DT_HAS_SIMCOM_A76XX_ENABLED)
 	help
 	  Use the default MTU size of 127 bytes for the CMUX module on certain modems.
 	  This must match the AT+CMUX commands in the modem_cellular driver.