fix(modem): Fixed mode transitions between any state and UNDEF

Closes espressif#320

Author: david-cermak

components/esp_modem/examples/modem_console/main/modem_console_main.cpp

@@ -235,7 +235,9 @@ extern "C" void app_main(void)
         if (c->get_count_of(&SetModeArgs::mode)) {
             auto mode = c->get_string_of(&SetModeArgs::mode);
             modem_mode dev_mode;
-            if (mode == "CMUX1") {
+            if (mode == "UNDEF") {
+                dev_mode = esp_modem::modem_mode::UNDEF;
+            } else if (mode == "CMUX1") {
                 dev_mode = esp_modem::modem_mode::CMUX_MANUAL_MODE;
             } else if (mode == "CMUX2") {
                 dev_mode = esp_modem::modem_mode::CMUX_MANUAL_EXIT;

components/esp_modem/src/esp_modem_dce.cpp

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -96,6 +96,11 @@ bool DCE_Mode::set_unsafe(DTE *dte, ModuleIf *device, Netif &netif, modem_mode m
 {
     switch (m) {
     case modem_mode::UNDEF:
+        if (!dte->set_mode(m)) {
+            return false;
+        }
+        mode = m;
+        return true;
     case modem_mode::DUAL_MODE: // Only DTE can be in Dual mode
         break;
     case modem_mode::COMMAND_MODE:
@@ -151,7 +156,7 @@ bool DCE_Mode::set_unsafe(DTE *dte, ModuleIf *device, Netif &netif, modem_mode m
         mode = modem_mode::CMUX_MANUAL_MODE;
         return true;
     case modem_mode::CMUX_MANUAL_EXIT:
-        if (mode != modem_mode::CMUX_MANUAL_MODE) {
+        if (mode != modem_mode::CMUX_MANUAL_MODE && mode != modem_mode::UNDEF) {
             return false;
         }
         if (!dte->set_mode(m)) {
@@ -160,20 +165,20 @@ bool DCE_Mode::set_unsafe(DTE *dte, ModuleIf *device, Netif &netif, modem_mode m
         mode = modem_mode::COMMAND_MODE;
         return true;
     case modem_mode::CMUX_MANUAL_SWAP:
-        if (mode != modem_mode::CMUX_MANUAL_MODE) {
+        if (mode != modem_mode::CMUX_MANUAL_MODE && mode != modem_mode::UNDEF) {
             return false;
         }
         if (!dte->set_mode(m)) {
             return false;
         }
         return true;
     case modem_mode::CMUX_MANUAL_DATA:
-        if (mode != modem_mode::CMUX_MANUAL_MODE) {
+        if (mode != modem_mode::CMUX_MANUAL_MODE && mode != modem_mode::UNDEF) {
             return false;
         }
         return transitions::enter_data(*dte, *device, netif);
     case modem_mode::CMUX_MANUAL_COMMAND:
-        if (mode != modem_mode::CMUX_MANUAL_MODE) {
+        if (mode != modem_mode::CMUX_MANUAL_MODE && mode != modem_mode::UNDEF) {
             return false;
         }
         return transitions::exit_data(*dte, *device, netif);

components/esp_modem/src/esp_modem_dte.cpp

@@ -151,10 +151,14 @@ command_result DTE::command(const std::string &cmd, got_line_cb got_line, uint32
 
 bool DTE::exit_cmux()
 {
+    if (!cmux_term) {
+        return false;
+    }
     if (!cmux_term->deinit()) {
         return false;
     }
     exit_cmux_internal();
+    cmux_term.reset();
     return true;
 }
 
@@ -174,6 +178,10 @@ void DTE::exit_cmux_internal()
 
 bool DTE::setup_cmux()
 {
+    if (cmux_term) {
+        ESP_LOGE("esp_modem_dte", "Cannot setup_cmux(), cmux_term already exists");
+        return false;
+    }
     cmux_term = std::make_shared<CMux>(primary_term, std::move(buffer));
     if (cmux_term == nullptr) {
         return false;
@@ -198,6 +206,11 @@ bool DTE::setup_cmux()
 
 bool DTE::set_mode(modem_mode m)
 {
+    // transitions (any) -> UNDEF
+    if (m == modem_mode::UNDEF) {
+        mode = m;
+        return true;
+    }
     // transitions (COMMAND|UNDEF) -> CMUX
     if (m == modem_mode::CMUX_MODE) {
         if (mode == modem_mode::UNDEF || mode == modem_mode::COMMAND_MODE) {
@@ -246,7 +259,7 @@ bool DTE::set_mode(modem_mode m)
         return false;
     }
     // manual CMUX transitions: Exit CMUX
-    if (m == modem_mode::CMUX_MANUAL_EXIT && mode == modem_mode::CMUX_MANUAL_MODE) {
+    if (m == modem_mode::CMUX_MANUAL_EXIT && (mode == modem_mode::CMUX_MANUAL_MODE || mode == modem_mode::UNDEF))  {
         if (exit_cmux()) {
             mode = modem_mode::COMMAND_MODE;
             return true;
@@ -255,7 +268,7 @@ bool DTE::set_mode(modem_mode m)
         return false;
     }
     // manual CMUX transitions: Swap terminals
-    if (m == modem_mode::CMUX_MANUAL_SWAP && mode == modem_mode::CMUX_MANUAL_MODE) {
+    if (m == modem_mode::CMUX_MANUAL_SWAP && (mode == modem_mode::CMUX_MANUAL_MODE || mode == modem_mode::UNDEF)) {
         secondary_term.swap(primary_term);
         set_command_callbacks();
         return true;