How to re-provision ESP with wifi credentials without forcing a reboot?

[karunt]

ESP documentation sates:
If provisioning state needs to be reset, any of the following approaches may be taken :

the associated part of NVS partition has to be erased manually

main application must implement some logic to call esp_wifi_ APIs for erasing the credentials at runtime

main application must implement some logic to force start the provisioning irrespective of the provisioning state

If I take the first approach (manually erase associated part of NVS partition) and then try to resend wifi credentials, I still get an error because prov_ctx->prov_state is WIFI_PROV_STATE_SUCCESS, so I'm unable to re-provision the chip with new credentials other than manually forcing a restart by calling

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ESP_ERROR_CHECK(wifi_prov_mgr_start_provisioning(security, pop, service_name, service_key))

. Here's my code to erase NVS:

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   ESP_ERROR_CHECK(nvs_flash_erase());
            esp_err_t ret = nvs_flash_init();
            if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
                ESP_ERROR_CHECK(nvs_flash_erase());
                ESP_ERROR_CHECK(nvs_flash_init());
            }
            wifi_config_t wifi_cfg_empty;
            memset(&wifi_cfg_empty, 0, sizeof(wifi_config_t));
            esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_cfg_empty);

Any idea how to accomplish this simply after erasing associated part of NVS partition?

[ESP_Mahavir]

Hi Karun,

- Provisioning manager has an API to reset persistent credentials `wifi_prov_mgr_reset_provisioning()`, please refer to usage at https://github.com/espressif/esp-idf/bl ... ain.c#L233
- Additionally there is also an API to reset provisioning manager state in case of failure `wifi_prov_mgr_reset_sm_state_on_failure()` which resets internal state machine and also clears any NVS credentials, please refer to usage at https://github.com/espressif/esp-idf/bl ... main.c#L74

For your case, you can use first API to clear WiFi credentials from NVS partition. Since in your case, provisioning was successful, 2nd API may not help. In this case, I would recommend that you stop WiFi provisioning manager service and then restart it. That should help to achieve your aim.

Please let us know if you face any issues here.

Thanks.

[karunt]

Thank you. So `wifi_prov_mgr_reset_provisioning()` calls `esp_wifi_restore()`, but where can I find the code for `esp_wifi_restore()`? Doesn't appear to be anywhere in the files within the components folder besides being defined in esp_wifi.h. Or is the code for esp_wifi_restore hidden and not available to users to understand and possibly customize?

[ESP_Mahavir]

Hello,

`esp_wifi_restore` API comes from WiFi library (no source code) and its documented at https://github.com/espressif/esp-idf/bl ... #L322-L335. It is responsible to reset WiFi settings from NVS to default values. If you need anything in addition, you may use direct NVS APIs.

Hope this helps!

[karunt]

I was able to find `esp_wifi_restore()` in the esp_wifi library, but still trying to get my arms around how it resets NVS values to default if there's no code besides just being defined in the esp_wifi library. I see the 4 other apis it uses (`esp_wifi_set_bandwidth`,
`esp_wifi_set_protocol`, `esp_wifi_set_config_related`, and `esp_wifi_set_mode`) to reset the values to default, but again, without a code that calls those 4 apis, how does `esp_wifi_restore` accomplish its goal? That's confusing me quite a bit. Thanks.

[karunt]

Follow up question to your proposal to use esp_wifi_restore() to reprovision ESP chip. When I execute ble write to write a command to the characteristic associated with the custom handler to reboot the chip, my write function always results in an error. It appears what's happening is that the response to the ble write command isn't sent back because the chip is forced to restore and reboot. How to avoid this situation? I mean, I'd like for ESP32 to respond to the write command to let the client side know that the write operation was successful, then begin the restore/reboot process. Here's my custom handler code:

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esp_err_t custom_prov_data_handler(uint32_t session_id, const uint8_t *inbuf, ssize_t inlen,
                                          uint8_t **outbuf, ssize_t *outlen, void *priv_data)
{   
    if (strncmp((char *)inbuf, "reboot", inlen) == 0) {
        ESP_LOGI(TAG, "Received data: %.*s", inlen, (char *)inbuf);
        char service_name[12];
        get_device_service_name(service_name, sizeof(service_name));
        wifi_prov_security_t security = WIFI_PROV_SECURITY_0;
        const char *pop = "abcd1234";
        const char *service_key = NULL;
        wifi_prov_mgr_stop_provisioning();
        ESP_ERROR_CHECK(esp_wifi_restore());
        ESP_ERROR_CHECK(wifi_prov_mgr_start_provisioning(security, pop, service_name, service_key));
    }

    char response[] = "SUCCESS";
    *outbuf = (uint8_t *)strdup(response);
    if (*outbuf == NULL) {
        ESP_LOGE(TAG, "System out of memory");
        return ESP_ERR_NO_MEM;
    }
    *outlen = strlen(response) + 1; // +1 for NULL terminating byte

    return ESP_OK;
}

[gulliverr]

Original question (and my request too) is to avoid the reboot and re-accept credentials. I'm on BLE too and if the user "accidentally" enters wrong WiFi password it makes much sense (after an event or even timeout && ! IP_EVENT_STA_GOT_IP) to clear the state and re-accept new credentials.
Modifying the component's source does not appeal to me as it is asking for (future) trouble. I'm on IDF 4.2.1 which I know is prehistoric...

[ESP_laukik-hase]

Hello,

Support for re-provisioning the device for new credentials once the device had been successfully provisioned before has been added with the commit 9bc1cc7 in ESP-IDF. Please check out the wifi_prov_mgr example for details.

Also, an additional endpoint has been added for controlling the Wi-Fi provisioning state with two commands ctrl_reset and ctrl_reprov - refer to this for more details. Note that this endpoint is accessible only with the esp_prov tool for now.

Thanks,
Laukik

[gulliverr]

Thank you but this commit is for re-provisioning if initial attempt was successful!
My problem is how to re-provision the device if the user mistyped his WiFi password without having to restart the device (and reconnect BLE). And I'm also on IDF 4.2.1 which is probably a dealbreaker straight away

[ESP_laukik-hase]

Hello,

In the wifi_prov_mgr example, by default, when incorrect credentials are enabled, the example tries connecting with the AP for a number of attempts and resets the state machine (see the config options here and the corresponding API here). This allows reprovisioning the device again without having to reset it or re-establish the BLE transport connection. However, this feature is available only on ESP-IDF v4.3.1 and above.


Thanks,
Laukik