FAQ
TL;DR: Build an ESP32 softAP web UI with POST/GET in ESP‑IDF. Since v4.1, "ESP‑NETIF replaces TCP/IP Adapter", so update APIs and examples before compiling. Use esp_http_server for handlers. ["TCP/IP Adapter Migration (ESP‑IDF)"]
Why it matters: It avoids deprecation warnings and link errors while enabling a clean POST/GET workflow in ESP‑IDF.
For: ESP‑IDF users who want a softAP-hosted web page with form/JSON exchange, without Arduino.
Quick Facts
- ESP‑IDF v4.1+ adopts ESP‑NETIF; legacy tcpip_adapter APIs are deprecated and require migration. ["TCP/IP Adapter Migration (ESP‑IDF)"]
- ESP32 SoftAP supports up to 10 client stations; default max_connection is typically 4. Tune for memory. ["ESP‑IDF Wi‑Fi API"]
- Check your ESP‑IDF version in components/esp_common/include/esp_idf_version.h. [Elektroda, khoam, post #19192912]
- If you copy an example, update PROJECT_NAME in build files to match the new folder to prevent path errors. [Elektroda, dondu, post #19192477]
- During the referenced thread, v4.2 was the latest stable release; prefer a tagged release over master. ["ESP‑IDF v4.2 Release"]
How do I create an ESP32 softAP that serves a web page with POST and GET in ESP‑IDF?
Configure Wi‑Fi in AP mode, then start the HTTP server and register URI handlers. Use esp_http_server for lightweight endpoints. Keep handlers small and non‑blocking. How‑To: 1. Start Wi‑Fi AP, then httpd_start(). 2. Register /get and /post with httpd_register_uri_handler(). 3. Parse query or body, respond with httpd_resp_send(). ["ESP‑IDF HTTP Server"]
Which ESP‑IDF changes break older softAP examples, and how do I update them?
ESP‑IDF v4.1 transitioned networking glue to ESP‑NETIF. Replace tcpip_adapter calls with esp_netif APIs. Initialize with esp_netif_init, then create the default AP netif. Expert note: "ESP‑NETIF replaces the legacy TCP/IP Adapter." Update includes and function names, then rebuild. ["TCP/IP Adapter Migration (ESP‑IDF)"]
Why does the softAP example fail after I copy it to a new folder?
A mismatched PROJECT_NAME can break build paths. Fix by aligning the project name with the new folder. How‑To: 1. Set PROJECT_NAME in your build file (CMake/Make). 2. Clean the build directory. 3. Reconfigure and compile. [Elektroda, dondu, post #19192477]
How do I check my ESP‑IDF version?
Open components/esp_common/include/esp_idf_version.h in your ESP‑IDF tree. Inspect the version macros for MAJOR, MINOR, and PATCH numbers. This verifies if you use a stable tag or a development branch. [Elektroda, khoam, post #19192912]
Is ESP‑IDF v4.3 stable? Which release should I target?
During the referenced discussion, v4.2 was the latest stable release. Use tagged releases for production instead of master. Check the release notes and tag your toolchain to match. This minimizes unexpected API drift and warnings. ["ESP‑IDF v4.2 Release"]
I get deprecation warnings about tcpip_adapter. What should I change?
Replace tcpip_adapter_init and friends with esp_netif_init and esp_netif_create_default_wifi_ap. Update event and DHCP handling through ESP‑NETIF. Maintain the same Wi‑Fi stack calls around the new netif layer. This clears deprecation messages in v4.1+. ["TCP/IP Adapter Migration (ESP‑IDF)"]
What’s the maximum number of clients my ESP32 SoftAP can accept?
ESP32 SoftAP supports up to 10 stations. The default max_connection is typically 4. Increase it in wifi_config_t.ap.max_connection if RAM and throughput allow. Higher counts can reduce throughput and stability on heavy traffic. ["ESP‑IDF Wi‑Fi API"]
I get "undefined reference" when calling launchSoftAp() from another file. Why?
The function is likely declared static, which limits linkage to one translation unit. Remove static or declare the prototype in a header included by the caller. Rebuild after cleaning. This resolves the undefined symbol during linking. [Elektroda, khoam, post #19188010]
How do I set the SoftAP network interface and IP using ESP‑NETIF?
Initialize ESP‑NETIF and create the default AP netif. Stop the DHCP server, set your desired IP/netmask/gateway, then restart DHCP. This approach replaces old tcpip_adapter calls and keeps your configuration forward‑compatible. ["TCP/IP Adapter Migration (ESP‑IDF)"]
How do I register GET and POST handlers correctly with esp_http_server?
Create httpd_uri_t entries with .method = HTTP_GET or HTTP_POST. In POST handlers, read the body with httpd_req_recv. Parse key‑value or JSON, then reply using httpd_resp_send or chunked responses. Keep handlers short to avoid watchdog resets. ["ESP‑IDF HTTP Server"]
What’s the quickest way to verify my SoftAP works before adding HTTP?
Flash the Wi‑Fi getting_started SoftAP example. Connect a phone or laptop to the SSID and confirm DHCP assignment. Watch the serial log for connection events and assigned IP. Then add the HTTP server once Wi‑Fi is stable. ["ESP‑IDF Wi‑Fi Example: SoftAP"]
Can I implement this without Arduino libraries?
Yes. Use native ESP‑IDF components: Wi‑Fi, ESP‑NETIF, and esp_http_server. They provide full control of AP mode and HTTP endpoints. This avoids Arduino wrappers and aligns with Espressif’s recommended APIs for v4.1+. ["ESP‑IDF HTTP Server"]
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