*DRAFT:* AT Host Refactoring for pipe based architecture

app/CMakeLists.txt

@@ -28,6 +28,7 @@ target_sources_ifdef(CONFIG_SM_CMUX app PRIVATE src/sm_cmux.c)
 target_sources_ifdef(CONFIG_SM_GNSS app PRIVATE src/sm_at_gnss.c)
 target_sources_ifdef(CONFIG_SM_NRF_CLOUD app PRIVATE src/sm_at_nrfcloud.c)
 target_sources_ifdef(CONFIG_SM_MQTTC app PRIVATE src/sm_at_mqtt.c)
+target_sources_ifdef(CONFIG_SM_BUTTONS app PRIVATE src/buttons.c)
 
 add_subdirectory_ifdef(CONFIG_SM_CARRIER src/lwm2m_carrier)
 

app/Kconfig

@@ -211,6 +211,15 @@ config SM_MODEM_PIPE_TIMEOUT
 
 endif # SM_CMUX || SM_PPP
 
+config HEAP_MEM_POOL_ADD_SIZE_SM_AT
+	int "Additional heap memory pool size for AT Host"
+	default 16384 if SM_CMUX
+	default 8192
+	help
+	  Additional heap memory pool size required for AT Host.
+	  This value is added to the total heap memory pool size defined in
+	  CONFIG_HEAP_MEM_POOL_SIZE.
+
 if SM_MQTTC
 
 config SM_MQTTC_MESSAGE_BUFFER_LEN
@@ -254,6 +263,33 @@ config SM_PGPS_INJECT_FIX_DATA
 
 endif # SM_GNSS
 
+config SM_BUTTONS
+	bool "Button handling module"
+	depends on BOARD_NRF9151DK
+	depends on INPUT_GPIO_KEYS
+	help
+	  Module that handles button presses to send AT commands to the modem.
+
+if SM_BUTTONS
+
+config SM_BUTTON0_AT
+	string "AT command for button 0"
+	default "AT+CFUN=4"
+
+config SM_BUTTON1_AT
+	string "AT command for button 1"
+	default "AT+CFUN=1"
+
+config SM_BUTTON2_AT
+	string "AT command for button 2"
+	default "AT+CGATT=0"
+
+config SM_BUTTON3_AT
+	string "AT command for button 3"
+	default "AT+CGATT=1"
+
+endif # SM_BUTTONS
+
 module = SM
 module-str = serial modem
 source "$(ZEPHYR_BASE)/subsys/logging/Kconfig.template.log_config"

app/boards/nrf9151dk_nrf9151_ns.overlay

@@ -8,6 +8,9 @@
 	chosen {
 		ncs,sm-uart = &dtr_uart0;
 	};
+	buttons {
+		status = "okay";
+	};
 };
 
 /* DTR with DK */

app/prj.conf

@@ -42,6 +42,11 @@ CONFIG_AT_CMD_CUSTOM=y
 # Align the max FD entry to NRF_MODEM_MAX_SOCKET_COUNT(8)
 CONFIG_ZVFS_OPEN_MAX=8
 
+# Modem pipe
+CONFIG_MODEM_MODULES=y
+CONFIG_MODEM_PIPE=y
+CONFIG_MODEM_CMUX=y
+
 # Handle modem fault
 CONFIG_NRF_MODEM_LIB_ON_FAULT_APPLICATION_SPECIFIC=y
 
@@ -58,7 +63,6 @@ CONFIG_NRFX_TIMER=y
 
 # Stacks and heaps
 CONFIG_MAIN_STACK_SIZE=4096
-CONFIG_HEAP_MEM_POOL_SIZE=16384
 CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=4096
 CONFIG_AT_MONITOR_HEAP_SIZE=4096
 

app/src/buttons.c

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+#include <zephyr/input/input.h>
+#include <zephyr/logging/log.h>
+#include "sm_util.h"
+
+LOG_MODULE_REGISTER(buttons, LOG_LEVEL_DBG);
+
+static void button_handler(struct input_event *evt, void *user_data)
+{
+	if (evt->type != INPUT_EV_KEY || evt->value != 1) {
+		return;
+	}
+
+	int ret;
+	const char *at_cmd;
+
+	switch (evt->code) {
+	case INPUT_KEY_0:
+		at_cmd = CONFIG_SM_BUTTON0_AT;
+		break;
+	case INPUT_KEY_1:
+		at_cmd = CONFIG_SM_BUTTON1_AT;
+		break;
+	case INPUT_KEY_2:
+		at_cmd = CONFIG_SM_BUTTON2_AT;
+		break;
+	case INPUT_KEY_3:
+		at_cmd = CONFIG_SM_BUTTON3_AT;
+		break;
+	default:
+		return;
+	}
+
+	ret = sm_util_at_printf(at_cmd);
+	LOG_DBG("Sent AT command \"%s\" from button %d, ret=%d", at_cmd, evt->code, ret);
+}
+
+INPUT_CALLBACK_DEFINE(NULL, button_handler, NULL);

app/src/lwm2m_carrier/sm_at_carrier.c

@@ -15,14 +15,13 @@
 #include "sm_at_host.h"
 #include "sm_settings.h"
 #include "sm_util.h"
-#include "sm_at_carrier.h"
 
 LOG_MODULE_REGISTER(sm_carrier, CONFIG_SM_LOG_LEVEL);
 
 /* Static variable to report the memory free resource. */
 static int m_mem_free;
-
-struct k_work_delayable reconnect_work;
+static void reconnect_wk(struct k_work *work);
+static K_WORK_DELAYABLE_DEFINE(reconnect_work, reconnect_wk);
 
 /* Global functions defined in different files. */
 int lte_auto_connect(void);
@@ -967,15 +966,3 @@ static int do_carrier_send(enum at_parser_cmd_type, struct at_parser *parser,
 
 	return lwm2m_carrier_data_send(path, path_len);
 }
-
-int sm_at_carrier_init(void)
-{
-	k_work_init_delayable(&reconnect_work, reconnect_wk);
-
-	return 0;
-}
-
-int sm_at_carrier_uninit(void)
-{
-	return 0;
-}

app/src/lwm2m_carrier/sm_at_carrier_cfg.c

@@ -711,11 +711,14 @@ static int do_cfg_uri(enum at_parser_cmd_type, struct at_parser *parser, uint32_
 	return lwm2m_settings_server_uri_set(server_uri);
 }
 
-int sm_at_carrier_cfg_init(void)
+#if defined(CONFIG_SM_CARRIER_AUTO_STARTUP)
+static int sm_at_carrier_cfg_init(void)
 {
 	if (IS_ENABLED(CONFIG_SM_CARRIER_AUTO_STARTUP)) {
 		return lwm2m_settings_auto_startup_set(true);
 	}
 
 	return 0;
 }
+SYS_INIT(sm_at_carrier_cfg_init, APPLICATION, 0);
+#endif

app/src/main.c

@@ -16,16 +16,12 @@
 #include "sm_at_host.h"
 #include "sm_at_dfu.h"
 #include "sm_at_fota.h"
-#include "sm_settings.h"
 #include "sm_util.h"
 #include "sm_ctrl_pin.h"
+#include "sm_uart_handler.h"
 
 LOG_MODULE_REGISTER(sm, CONFIG_SM_LOG_LEVEL);
 
-#define SM_WQ_STACK_SIZE	KB(4)
-#define SM_WQ_PRIORITY		K_LOWEST_APPLICATION_THREAD_PRIO
-static K_THREAD_STACK_DEFINE(sm_wq_stack_area, SM_WQ_STACK_SIZE);
-
 struct k_work_q sm_work_q;
 
 NRF_MODEM_LIB_ON_INIT(lwm2m_init_hook, on_modem_lib_init, NULL);
@@ -147,22 +143,6 @@ static int bootloader_mode_init(void)
 	}
 	LOG_INF("Bootloader mode initiated successfully");
 
-	ret = sm_ctrl_pin_init();
-	if (ret) {
-		LOG_ERR("Failed to init ctrl_pin: %d", ret);
-		return ret;
-	}
-
-	k_work_queue_start(&sm_work_q, sm_wq_stack_area,
-		K_THREAD_STACK_SIZEOF(sm_wq_stack_area),
-		SM_WQ_PRIORITY, NULL);
-
-	ret = sm_at_host_bootloader_init();
-	if (ret) {
-		LOG_ERR("Failed to init at_host: %d", ret);
-		return ret;
-	}
-
 	ret = sm_at_send_str("Bootloader mode ready\r\n");
 	if (ret) {
 		LOG_ERR("Failed to send bootloader mode ready string: %d", ret);
@@ -236,37 +216,19 @@ int lte_auto_connect(void)
 	return err;
 }
 
-int start_execute(void)
+int main(void)
 {
-	int err;
-
-	LOG_INF("Serial Modem");
-
-	err = sm_ctrl_pin_init();
-	if (err) {
-		LOG_ERR("Failed to init ctrl_pin: %d", err);
-		return err;
-	}
-
-	k_work_queue_start(&sm_work_q, sm_wq_stack_area,
-		   K_THREAD_STACK_SIZEOF(sm_wq_stack_area),
-		   SM_WQ_PRIORITY, NULL);
-
-	/* This will send "READY" or "INIT ERROR" to UART so after this nothing
-	 * should be done that can fail
-	 */
-	err = sm_at_host_init();
-	if (err) {
-		LOG_ERR("Failed to init at_host: %d", err);
-		return err;
-	}
-
-	(void)lte_auto_connect();
+	static const struct k_work_queue_config cfg = {
+		.name = "sm_work_q",
+		.essential = true,
+	};
 
+	k_work_queue_init(&sm_work_q);
+	k_work_queue_run(&sm_work_q, &cfg);
 	return 0;
 }
 
-int main(void)
+static int sm_main(void)
 {
 	int ret;
 
@@ -275,13 +237,6 @@ int main(void)
 	nrf_power_resetreas_clear(NRF_POWER_NS, 0x70017);
 	LOG_DBG("RR: 0x%08x", rr);
 
-	sm_ctrl_pin_init_gpios();
-
-	/* Init and load settings */
-	if (sm_settings_init() != 0) {
-		LOG_WRN("Failed to init sm settings");
-	}
-
 	if (sm_bootloader_mode_requested) {
 		/* Clear bootloader mode flag */
 		ret = bootloader_mode_request(false);
@@ -293,7 +248,7 @@ int main(void)
 				LOG_ERR("Failed to initialize bootloader mode: %d", ret);
 				goto exit_reboot;
 			}
-			goto exit;
+			return ret;
 		}
 	}
 
@@ -309,7 +264,7 @@ int main(void)
 	if (ret) {
 		LOG_ERR("Modem library init failed, err: %d", ret);
 		if (ret != -EAGAIN && ret != -EIO) {
-			goto exit;
+			return ret;
 		} else if (ret == -EIO) {
 			LOG_ERR("Please program full modem firmware with the bootloader or "
 				"external tools");
@@ -327,14 +282,27 @@ int main(void)
 	}
 #endif
 
-	ret = start_execute();
-exit:
-	if (ret) {
-		LOG_ERR("Failed to start SM (%d). It's not operational!!!", ret);
+	if (!IS_ENABLED(CONFIG_SM_SKIP_READY_MSG)) {
+		/* Send Ready string to indicate that AT host is ready */
+		ret = sm_at_send_str(SM_SYNC_STR);
+		if (ret) {
+			return ret;
+		}
 	}
+
+	/* This is here and not earlier because in case of firmware
+	 * update it will send an AT response so the UART must be up.
+	 */
+	sm_fota_post_process();
+
+	(void)lte_auto_connect();
+
+	LOG_INF("Serial Modem");
+
 	return ret;
 
 exit_reboot:
 	LOG_PANIC();
 	sys_reboot(SYS_REBOOT_COLD);
 }
+SYS_INIT(sm_main, APPLICATION, 100);