# SLIP device client

(See the README.md file in the upper level 'examples' directory for more information about examples.)

## Overview

This provides SLIP support for connection to Contiki gateway devices, allowing the ESP platform board to be used to bridge between low-power networks and IP (Wifi / Ethernet).

## How to use example

### Hardware Required

To run this example, you need an ESP32 dev board (e.g. ESP32-WROVER Kit) or ESP32 core board (e.g. ESP32-DevKitC).
For test purpose, you also need a SLIP capable gateway device, such as anything running [Contiki](https://github.com/contiki-os/contiki) gateway firmware.
You can also try other modules as long as they implement the SLIP protocol (e.g. linux device with slip module loaded)

#### Setup a test SLIP device

It is possible to configure any device with linux and a serial interface
(e.g. raspberry PI or a PC with USB to serial bridge) to enable SLIP interface.

To test this example with such device, please follow these steps:

- Configure IPv4 mode in the example configuration menu

- Setup SLIP interface
```
slattach -v -L -s 115200 -p slip /dev/ttyAMA0
```
where the `/dev/ttyAMA0` is the device's serial port

- Configure IP addresses
```
ifconfig sl0 10.0.0.1 dstaddr 10.0.0.2
```
where the `10.0.0.2` is IPv4 address of the ESP platform board

- Send and receive back UDP packets, as the example implements UDP echo server
```
nc -u 10.0.0.2 5678
```

#### Pin Assignment

**Note:** The following pin assignments are used by default which can be changed in menuconfig.

| ESP32  | Gateway |
| ------ | -------------- |
| GPIO4  | RX             |
| GPIO36 | TX             |
| GND    | GND            |
| 3v3    | VCC            |

### Configure the project

Open the project configuration menu (`idf.py menuconfig`). Then go into `Example Configuration` menu.

- Choose the RX and TX pins
- Choose port number and IP protocol for socket udp server
For use in external projects `SLIP support` must be enabled under the `components/lwip` menu.


### Build and Flash

Run `idf.py -p PORT flash monitor` to build and flash the project..

(To exit the serial monitor, type ``Ctrl-]``.)

See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.



## Troubleshooting

1. Invalid slip packets

Many slip devices use additional messages for things like ipv6 prefix configuration (or sending log messages over the SLIP serial port). This is supported in the driver through the use of an `rx_filter` function that is called on receipt of all packets and can be used to filter packets prior to passing them to the stack.

2. No packets received

The first layer to check is the serial port, you can enable debugging of the SLIP component by setting the global log level to `DEBUG`, or changing the slip component log levbel with `esp_log_level_set("esp-netif_lwip-slip", ESP_LOG_DEBUG);`

(For any technical queries, please open an [issue](https://github.com/espressif/esp-idf/issues) on GitHub. We will get back to you as soon as possible.)