fix esp_modem switch mode timeout

Closes https://github.com/espressif/esp-idf/issues/3506
Closes https://github.com/espressif/esp-idf/issues/4324

examples/protocols/pppos_client/components/modem/include/esp_modem_dce.h

@@ -52,7 +52,7 @@ typedef struct modem_dte modem_dte_t;
  */
 #define MODEM_COMMAND_TIMEOUT_DEFAULT (500)      /*!< Default timeout value for most commands */
 #define MODEM_COMMAND_TIMEOUT_OPERATOR (75000)   /*!< Timeout value for getting operator status */
-#define MODEM_COMMAND_TIMEOUT_MODE_CHANGE (3000) /*!< Timeout value for changing working mode */
+#define MODEM_COMMAND_TIMEOUT_MODE_CHANGE (5000) /*!< Timeout value for changing working mode */
 #define MODEM_COMMAND_TIMEOUT_HANG_UP (90000)    /*!< Timeout value for hang up */
 #define MODEM_COMMAND_TIMEOUT_POWEROFF (1000)    /*!< Timeout value for power down */
 

examples/protocols/pppos_client/components/modem/src/esp_modem.c

@@ -387,6 +387,8 @@ modem_dte_t *esp_modem_dte_init(const esp_modem_dte_config_t *config)
     res = uart_driver_install(esp_dte->uart_port, CONFIG_EXAMPLE_UART_RX_BUFFER_SIZE, CONFIG_EXAMPLE_UART_TX_BUFFER_SIZE,
                               CONFIG_EXAMPLE_UART_EVENT_QUEUE_SIZE, &(esp_dte->event_queue), 0);
     MODEM_CHECK(res == ESP_OK, "install uart driver failed", err_uart_config);
+    res = uart_set_rx_timeout(esp_dte->uart_port, 1);
+    MODEM_CHECK(res == ESP_OK, "set rx timeout failed", err_uart_config);
 
     MODEM_CHECK(uart_param_config(esp_dte->uart_port, &uart_config) == ESP_OK, "config uart parameter failed", err_uart_config);
     if (config->flow_control == MODEM_FLOW_CONTROL_HW) {