samples: net: Create sample app for GSM modems

Sample app compiled with the GSM modem driver enabling PPP.

This sample was tested with a Reel Board UART_1 connected via the
external board/connector and a FONA 808 modem. Reel board specific
suppor is found in boards/.

Signed-off-by: Patrik Flykt <patrik.flykt@intel.com>

samples/net/gsm_modem/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+# DTS overlay files must include full path name
+#set(DTC_OVERLAY_FILE "${CMAKE_CURRENT_SOURCE_DIR}/sam_e70_xplained.overlay")
+
+cmake_minimum_required(VERSION 3.13.1)
+
+include($ENV{ZEPHYR_BASE}/cmake/app/boilerplate.cmake NO_POLICY_SCOPE)
+project(fona808)
+
+target_sources(app PRIVATE src/main.c)

samples/net/gsm_modem/boards/reel_board.conf

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+# Reel board UART
+CONFIG_UART_1_NRF_UARTE=y

samples/net/gsm_modem/frdm_uart2_dts.overlay

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+/*
+ * UART 2 is configured on FRDM pins PTD0, rts; PTD1, cts; PTD2, rx; PTD3, tx
+ * see https://www.nxp.com/docs/en/data-sheet/K64P144M120SF5.pdf chapter 5.1,
+ * page 74
+ */
+&uart2 {
+	status = "okay";
+	current-speed = <115200>;
+};

samples/net/gsm_modem/prj.conf

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+
+# UART support
+CONFIG_SERIAL=y
+
+# GSM modem support
+CONFIG_MODEM=y
+CONFIG_MODEM_GSM_PPP=y
+CONFIG_MODEM_GSM_UART_NAME="UART_1"
+
+# PPP networking support
+CONFIG_NET_PPP=y
+CONFIG_NET_L2_PPP=y
+CONFIG_NET_NATIVE=y
+CONFIG_NETWORKING=y
+
+CONFIG_NET_L2_PPP_TIMEOUT=10000
+
+# IPv4 enables PPP IPCP support
+CONFIG_NET_IPV4=y
+CONFIG_NET_IPV6=n
+
+# Network management events
+CONFIG_NET_CONNECTION_MANAGER=y
+
+# Log buffers, modem and PPP
+CONFIG_LOG=y
+CONFIG_NET_LOG=y
+#CONFIG_LOG_BUFFER_SIZE=16384
+#CONFIG_LOG_STRDUP_BUF_COUNT=200
+#CONFIG_MODEM_LOG_LEVEL_DBG=y
+#CONFIG_NET_PPP_LOG_LEVEL_DBG=y
+#CONFIG_NET_L2_PPP_LOG_LEVEL_DBG=y
+#CONFIG_NET_MGMT_EVENT_LOG_LEVEL_DBG=y
+#CONFIG_NET_CONNECTION_MANAGER_LOG_LEVEL_DBG=y

samples/net/gsm_modem/src/main.c

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+/*
+ * Copyright (c) 2020, Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <sys/printk.h>
+#include <drivers/uart.h>
+#include <net/net_mgmt.h>
+#include <net/net_event.h>
+#include <net/net_conn_mgr.h>
+
+#include <logging/log.h>
+LOG_MODULE_REGISTER(sample_gsm_ppp, LOG_LEVEL_DBG);
+
+static struct net_mgmt_event_callback mgmt_cb;
+
+static void event_handler(struct net_mgmt_event_callback *cb,
+			  u32_t mgmt_event, struct net_if *iface)
+{
+	if ((mgmt_event & (NET_EVENT_L4_CONNECTED
+			   | NET_EVENT_L4_DISCONNECTED)) != mgmt_event) {
+		return;
+	}
+
+	if (mgmt_event == NET_EVENT_L4_CONNECTED) {
+		LOG_INF("Network connected");
+		return;
+	}
+
+	if (mgmt_event == NET_EVENT_L4_DISCONNECTED) {
+		LOG_INF("Network disconnected");
+		return;
+	}
+}
+
+int main(void)
+{
+	struct device *uart_dev = device_get_binding(CONFIG_MODEM_GSM_UART_NAME);
+
+	LOG_INF("%s: booted board '%s' APN '%s' UART '%s' device %p",
+		__func__, CONFIG_BOARD, CONFIG_MODEM_GSM_APN,
+		CONFIG_MODEM_GSM_UART_NAME, uart_dev);
+
+	net_mgmt_init_event_callback(&mgmt_cb, event_handler,
+				     NET_EVENT_L4_CONNECTED |
+				     NET_EVENT_L4_DISCONNECTED);
+	net_mgmt_add_event_callback(&mgmt_cb);
+
+	return 0;
+}