chat AT over TTY

Demonstrates AT chat functionality over a TTY device. This is useful with AT modems, for example, to establish a pppd connection (see the related pppd example). Moreover, some AT modems – such as ones made by u-blox – have an internal TCP/IP stack, often with an implementation of TLS/SSL. In such cases the chat utility can be used to configure the internal TCP/IP stack, establish socket connections, set up security (e.g., download base64-encoded certificates to the modem), and perform data exchange through sockets over the TTY device.

Useful configuration parameters:

• CONFIG_EXAMPLES_CHAT_PRESET[0..3] – preset chat scripts.

• CONFIG_EXAMPLES_CHAT_TTY_DEVNODE – TTY device node name.

• CONFIG_EXAMPLES_CHAT_TIMEOUT_SECONDS – default receive timeout.