ATWINC15x0 WiFi module driver

Network device driver for the Microchip ATWINC15x0 WiFi Module. More...

Detailed Description

Network device driver for the Microchip ATWINC15x0 WiFi Module.

Author

Gunar Schorcht gunar.nosp@m.@sch.nosp@m.orcht.nosp@m..net

Introduction

This module implements a netdev device driver for the Microchip ATWINC15x0 WiFi module. The ATWINC15x0 WiFi module is widely used as WiFi interface on various boards and extension boards. Examples are:

• Adafruit Feather M0 WiFi (also supported by RIOT)
• ATWIN1500-XPRO for the extension of Atmel Xplained PRO boards (also supported by RIOT)
• Adafruit ATWINC1500 WiFi breakout
• Watterott ATWINC1500-Breakout

Since the ATWINC15x0 WiFi module is also the only module supported by the standard Arduino WiFi101 library, there are a number of Arduino shields with the ATWINC15x0 WiFi module, e.g. Adafruit WINC1500 WiFi Shield for Arduino.

Using this 'netdev' driver together with an ATWINC15x0 WiFi module enables the connection via WiFi in RIOT.

Microchip ATWINC15x0 WiFi module

The ATWINC15x0 WiFi module is a low-power IEEE 802.11 b/g/n module with a bandwidth of 20 MHz in the 2,4 GHz ISM band. It supports the IEEE 802.11i/WPA2 personal and enterprise modes. In enterprise mode it supports

• EAP-TLS
• EAP-PEAPv0/1 with TLS
• EAP-TTLSv0 with MSCHAPv2
• EAP-PEAPv0/1 with MSCHAPv2

The WiFi module ATWINC15x0 is connected via SPI and supports SPI clock speeds of up to 48 MHz. Although the module also has an I2C and a UART interface, these interfaces are only used for debugging.

The ATWINC15x0 WiFi module implements a complete TCP/IP protocol stack which is not used in RIOT.

Driver Details

The ATWINC15x0 WiFi netdev driver doesn't directly use the ATWINC15x0 WiFi module. Instead, it uses the ATWINC15x0 vendor driver WINC1500 Wifi. from Microchip's Advanced Software Framework. For that purpose, the Arduino WiFi101 library which also includes this vendor library is used as a package.

Although the ATWINC15x0 vendor driver is complex and quite large, there is no other way to do it because the ATWINC15x0 WiFi module's programming interface is not documented. At the very least, the ATWINC15x0 WiFi netdev driver uses only those parts of the vendor driver that are absolutely necessary.

The ATWINC15x0 vendor driver consists of several parts:

• the M2M WiFi library, which implements high-level WiFi connection management Functions
• the HIF (Host Interface) library, which implements the interface with the ATWINC15x0 module
• the BSP (Bus Support Package) as an abstraction layer for platform-specific Functions
• the bus wrapper interface for access to the SPI

In addition to these parts, the ATWINC15x0 vendor driver contains a socket library and a library for accessing the SPI flash of the ATWINC15x0 module, but these are not used in RIOT.

The ATWINC15x0 WiFi netdev driver replaces the BSP and the Bus Wrapper Interface by RIOT specific parts and interacts with ATWINC15x0 vendor driver as shown in the following figure.

+-----------------+        +---------------+   +----------+    +------------+
| RIOT ATWINC15x0 |        |   ATWINC15x0  |   | RIOT Bus |    | ATWINC15x0 |
|  netdev driver  |        | vendor driver |   |  Wrapper |    |   module   |
+-----------------+        +---------------+   +----------+    +------------+
        |                          |                |                |
        |      m2m_wifi_func       |    command     |  SPI(command)  |
        |------------------------->|--------------->|--------------->|
        |          return          |                |                |
        |<-------------------------|                |                |
        |                          |                |                |
        |                          |                |                |
        |                          |                |                |
        |<------------------------------- IRQ -----------------------|
        |                          |                |                |
        |  m2m_wifi_handle_events  |     request    |  SPI(request)  |
        |------------------------->|--------------->|--------------->|
        |                          |     response   | SPI(response)  |
        |    atwinc15x0_wifi_cb    |<---------------|<---------------|
        |<-------------------------|                |                |
        |                          |                |                |
        |                          |                |                |
        |                          |                |                |
        |                          |                |                |
        |<------------------------------- IRQ -----------------------|
        |                          |                |                |
        |  m2m_wifi_handle_events  |     request    |  SPI(request)  |
        |------------------------->|--------------->|--------------->|
        |                          |     response   | SPI(response)  |
        |    atwinc15x0_eth_cb     |<---------------|<---------------|
        |<-------------------------|                |                |

As shown, the ATWINC15x0 WiFi module operates asynchronously. This means that when an API function of the ATWINC15x0 driver is called, it simply sends a command to the ATWINC15x0 WiFi module and returns immediately. The command is then executed asynchronously by the ATWINC15x0 WiFi module. As soon as the execution of the command is completed or one or more events are pending, the module interrupts the host. Since the ISR is executed in the interrupt context, the ATWINC15x0 'netdev' driver simply indicates that an interrupt has occurred. The interrupt is handled later in the thread context by calling 'm2m_wifi_handle_events'. This in turn fetches available information from the ATWINC15x0 WiFi module and then calls various callback functions according to the state, all of which are executed in the thread context.

Configuration

The ATWINC15x0 'netdev' driver requires the configuration ATWINC15x0 WiFi module as WiFi settings:

Hardware Configuration

The default configuration is defined in atwinc15x0_params.h and can be overridden either by the board definition or by environment variables in make command line.

Symbol	Default	Description
ATWINC15X0_PARAM_SPI	SPI_DEV(0)	Used SPI device
ATWINC15X0_PARAM_SPI_CLK	SPI_CLK_10MHZ	Used SPI clock speed
ATWINC15X0_PARAM_SSN_PIN	GPIO_PIN(1, 4)	SPI slave select pin
ATWINC15X0_PARAM_RESET_PIN	GPIO_PIN(4, 3)	RESET pin
ATWINC15X0_PARAM_IRQ_PIN	GPIO_PIN(7, 4)	IRQ pin
ATWINC15X0_PARAM_CHIP_EN_PIN	GPIO_UNDEF	CHIP_EN pin
ATWINC15X0_PARAM_WAKE_PIN	GPIO_UNDEF	WAKE pin

WiFi Configuration

At the moment only WPA2 Personal Mode is supported. The required settings are:

Parameter	Default	Description
WIFI_SSID	"RIOT_AP"	SSID of the AP to be used.
WIFI_PASS	-	Passphrase used for the AP as clear text (max. 64 chars).

The following example shows the make command with the setting of different GPIOs and the WiFi parameters.

USEMODULE='atwinc15x0' \
CFLAGS='-DWIFI_SSID=\"ssid\" -DWIFI_PASS=\"pass\" \
        -DATWINC15X0_PARAM_SSN_PIN=GPIO_PIN\‍(1,6\‍) \
        -DATWINC15X0_PARAM_RESET_PIN=GPIO_PIN\‍(1,4\‍) \
        -DATWINC15X0_PARAM_IRQ_PIN=GPIO_PIN\‍(0,8\‍)' \
make BOARD=... -C examples/gnrc_networking flash term

Files
file	atwinc15x0_internal.h
	Internal definitions for the ATWINC15x0 WiFi netdev driver.
file	atwinc15x0_params.h
	Default configuration for the ATWINC15x0 WiFi netdev driver.