<alp/iot.h> — Wi-Fi & MQTT

Connectivity helpers for putting an E1M module on the network.

Header

#include <alp/iot.h>

Wi-Fi station

alp_wifi_t *wifi = alp_wifi_open(&(alp_wifi_config_t){
    .mode = ALP_WIFI_MODE_STATION,
});

alp_wifi_connect(wifi, &(alp_wifi_credentials_t){
    .ssid     = "MyNetwork",
    .password = "secret",
    .security = ALP_WIFI_SECURITY_WPA2,
});

while (!alp_wifi_is_connected(wifi)) {
    k_msleep(100);
}

alp_wifi_close(wifi);

On AEN this flows through the CC3501E coprocessor. On V2N it flows through the on-module Murata module. The application API is identical across silicon families.

MQTT

alp_mqtt_t *mqtt = alp_mqtt_open(&(alp_mqtt_config_t){
    .broker_uri = "mqtt://broker.example.com:1883",
    .client_id  = "alp-device-001",
});

alp_mqtt_connect(mqtt);
alp_mqtt_publish(mqtt, "sensors/temperature", "23.5", 4, ALP_MQTT_QOS_0);

void on_message(const char *topic, const uint8_t *payload, size_t len, void *user) {
    /* handle incoming message */
}
alp_mqtt_subscribe(mqtt, "actuators/+/cmd", ALP_MQTT_QOS_1, on_message, NULL);

// Drive the loop from your main thread, or spawn a worker
while (1) {
    alp_mqtt_loop(mqtt, 100);   // process pending events, 100 ms budget
}

alp_mqtt_close(mqtt);

TLS (mqtts://)

alp_mqtt_t *mqtt = alp_mqtt_open(&(alp_mqtt_config_t){
    .broker_uri = "mqtts://broker.example.com:8883",
    .client_id  = "alp-device-001",
    .tls = &(alp_mqtt_tls_config_t){
        .ca_path   = "/etc/ssl/certs",
        .cert_path = "/etc/alp/device.crt",
        .key_path  = "/etc/alp/device.key",
    },
});

The Yocto backend routes TLS through OpenSSL (mosquitto_tls_set); the Zephyr backend uses MbedTLS configured via <alp/security.h>.

:::warning mqtts:// now fails closed on a non-TLS build v0.10 fixes a silent plaintext downgrade (GHSA-gqjv-932h-c5gm). The Zephyr MQTT backend, when CONFIG_MQTT_LIB_TLS was disabled, discarded the parsed TLS result and always selected a non-secure transport — transmitting an mqtts:// connection's credentials and payloads in plaintext while the app believed the scheme enforced TLS.

An mqtts:// broker URI on a build without CONFIG_MQTT_LIB_TLS is now rejected with ALP_ERR_NOSUPPORT before any connection is attempted. If you relied on the old behaviour, you were not getting TLS — enable CONFIG_MQTT_LIB_TLS or switch the scheme to mqtt:// deliberately. :::

board.yaml

iot:
  wifi: true
  mqtt: true
  tls:  true

Default-initialiser macro

ALP_MQTT_CONFIG_DEFAULT(id) (v0.10) takes the broker URI as its identity argument:

alp_mqtt_config_t cfg = ALP_MQTT_CONFIG_DEFAULT("mqtt://broker.example.com:1883");
cfg.client_id = "e1m-node-1";

It sets broker_uri from id plus: client_id = NULL, username = NULL, password = NULL, keepalive_s = 60, clean_session = true, tls = NULL (no TLS).

See the shared macro contract for the C++ compound-literal caveat that applies to every ALP_*_CONFIG_DEFAULT.

See also

• <alp/security.h> — TLS / PSA Crypto
• <alp/ble.h> — BLE 5.4
• Examples: iot-connected-camera