Silicon Labs SLWSTK6220A starter kit

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Tip

When using this board with RIOT, set the BOARD variable to slwstk6220a in your Makefile. If you follow the standard RIOT project structure, your Makefile should look like this:

./Makefile

# name of your application
APPLICATION = hello-world

# Change this to your board if you want to build for a different board
BOARD ?= slwstk6220a

# This has to be the absolute path to the RIOT base directory:
RIOTBASE ?= $(CURDIR)/RIOT

include $(RIOTBASE)/Makefile.include

Support for Silicon Labs SLWSTK6220A starter kit

Overview

Silicon Labs EZR32WG 868MHz Wireless Starter Kit is equipped with the EFM32 microcontroller. It is specifically designed for low-power applications, having energy-saving peripherals, different energy modes and short wake-up times.

The starter kit is equipped with an Advanced Energy Monitor. This allows you to actively measure the power consumption of your hardware and code, in real-time.

Hardware

MCU

MCU	EZR32WG330F256R60
Family	ARM Cortex-M4F
Vendor	Silicon Labs
Vendor Family	EZR32 Wonder Gecko
RAM	32.0 KiB
Flash	256.0 KiB
EEPROM	no
Frequency	up to 48 MHz
FPU	yes
MPU	yes
DMA	12 channels
Timers	3x 16-bit + 1x 16-bit (low power)
ADCs, DACs	12-bit ADC, 12-bit DAC
UARTs	2x UART, 3x USART, 2x LEUART
SPIs	3x USART
I2Cs	2x
Vcc	1.98 V - 3.8 V
Datasheet	Datasheet
Manual	Manual
Board Manual	Board Manual
Board Schematic	Can be downloaded using Silicon Labs’ Simplicity Studio

Pinout

This is the pinout of the expansion header on the right side of the board. PIN 1 is the bottom-left contact when the header faces you horizontally.

	PIN	PIN
3V3	20	19	RES
5V	18	17	RES
PD6	16	15	PD7
PD5	14	13	PF13
PD4	12	11	PB11
PD3	10	9	PE1
PD2	8	7	PE0
PD1	6	5	PC7
PD0	4	3	PC6
VMCU	2	1	GND

Note: not all starter kits by Silicon Labs share the same pinout!

Note: some pins are connected to the board controller, when enabled!

Peripheral mapping

Peripheral	Number	Hardware	Pins	Comments
ADC	0	ADC0	CHAN0: internal temperature	Ports are fixed, 14/16-bit resolution not supported
DAC	0	DAC0	CHAN0: PB11	Ports are fixed, shared with I2C
HWCRYPTO	—	—		AES128/AES256 only
I2C	0	I2C0	SDA: PE0, SCL: PE1	I2C_SPEED_LOW and I2C_SPEED_HIGH clock speed deviate
PWM	0	TIMER0	CHAN0: PF6, CHAN1: PF7	Mapped to LED0 and LED1
RTT	—	RTC		Either RTT or RTC (see below)
RTC	—	RTC		Either RTC or RTT (see below)
SPI	0	USART1	MOSI: PD0, MISO: PD1, CLK: PD2
Timer	0	TIMER1 + TIMER2		TIMER1 is used as prescaler (must be adjacent)
	1	LETIMER0
UART	0	UART0	RX: PE1, TX: PE0	STDIO output
	1	LEUART0	RX: PD5, TX: PD4	Baud rate limited (see below)

User interface

Peripheral	Mapped to	Pin	Comments
Button	PB0	PE3
	PB1	PE2
LED	LED0	PF6	Yellow LED
	LED1	PF7	Yellow LED

Implementation Status

Device	ID	Supported	Comments
MCU	EZR32WG	yes	Power modes supported
Low-level driver	ADC	yes
	DAC	yes
	Flash	yes
	GPIO	yes	Interrupts are shared across pins (see reference manual)
	HW Crypto	yes
	I2C	yes
	PWM	yes
	RTC	yes	As RTT or RTC
	SPI	partially	Only master mode
	Timer	yes
	UART	yes	USART is shared with SPI. LEUART baud rate limited (see below)
	USB	no
LCD driver	LS013B7DH03	yes	Sharp Low Power Memory LCD via the U8g2 package
Temperature + humidity sensor	Si7021	yes	Silicon Labs Temperature + Humidity sensor

Board configuration

Board controller

The starter kit is equipped with a Board Controller. This controller provides a virtual serial port. The board controller is enabled via a GPIO pin.

By default, this pin is enabled. You can disable the board controller module by passing DISABLE_MODULE=silabs_bc to the make command.

Note: to use the virtual serial port, ensure you have the latest board controller firmware installed.

Note: the board controller always configures the virtual serial port at 115200 baud with 8 bits, no parity and one stop bit. This also means that it expects data from the MCU with the same settings.

The low power LCD is also used by the board controller when the DISP_SELECTED pin is low. This pin is not initialized by the board, so you have to ensure this pin is initialized by your application if you want to control the low power LCD.

Advanced Energy Monitor

This development kit has an Advanced Energy Monitor. It can be connected to the Simplicity Studio development software.

This development kit can measure energy consumption and correlate this with the code. It allows you to measure energy consumption on code-level.

The board controller is responsible for measuring energy consumption. For real-time code correlation, the CoreDebug peripheral will be configured to output MCU register data and interrupt data via the SWO port.

By default, this feature is enabled. It can be disabled by passing DISABLE_MODULE=silabs_aem to the make command.

Note that Simplicity Studio requires debug symbols to correlate code. RIOT-OS defaults to GDB debug symbols, but Simplicity Studio requires DWARF-2 debug symbols (-gdwarf-2 for GCC).

Clock selection

There are several clock sources that are available for the different peripherals. You are advised to read AN0004.0 to get familiar with the different clocks.

Source	Internal	Speed	Comments
HFRCO	Yes	14 MHz	Enabled during startup, changeable
HFXO	No	48 MHz
LFRCO	Yes	32.768 kHz
LFXO	No	32.768 kHz
ULFRCO	No	1 kHz	Not very reliable as a time source

The sources can be used to clock following branches:

Branch	Sources	Comments
HF	HFRCO, HFXO	Core, peripherals
LFA	LFRCO, LFXO	Low-power timers
LFB	LFRCO, LFXO, CORELEDIV2	Low-power UART

CORELEDIV2 is a source that depends on the clock source that powers the core. It is divided by 2 or 4 to not exceed maximum clock frequencies (EMLIB takes care of this).

The frequencies mentioned in the tables above are specific for this starter kit.

It is important that the clock speeds are known to the code, for proper calculations of speeds and baud rates. If the HFXO or LFXO are different from the speeds above, ensure to pass EFM32_HFXO_FREQ=freq_in_hz and EFM32_LFXO_FREQ=freq_in_hz to your compiler.

You can override the branch’s clock source by adding CLOCK_LFA=source to your compiler defines, e.g. CLOCK_LFA=cmuSelect_LFRCO.

Low-power peripherals

The low-power UART is capable of providing an UART peripheral using a low-speed clock. When the LFB clock source is the LFRCO or LFXO, it can still be used in EM2. However, this limits the baud rate to 9600 baud. If a higher baud rate is desired, set the clock source to CORELEDIV2.

Note: peripheral mappings in your board definitions will not be affected by this setting. Ensure you do not refer to any low-power peripherals.

RTC or RTT

RIOT-OS has support for Real-Time Tickers and Real-Time Clocks.

However, this board MCU family has support for a 24-bit Real-Time Counter only, which is a ticker only. A compatibility layer for ticker-to-calendar is available, but this includes extra code size to convert from timestamps to time structures and visa versa.

Configured at 1 Hz interval, the RTC will overflow each 194 days. When using the ticker-to-calendar mode, this interval is extended artificially.

Hardware crypto

This MCUs has support for hardware-accelerated AES128 and AES256.

A peripheral driver interface is proposed, but not yet implemented.

Usage of EMLIB

This port makes uses of EMLIB by Silicon Labs to abstract peripheral registers. While some overhead is to be expected, it ensures proper setup of devices, provides chip errata and simplifies development. The exact overhead depends on the application and peripheral usage, but the largest overhead is expected during peripheral setup. A lot of read/write/get/set methods are implemented as inline methods or macros (which have no overhead).

Another advantage of EMLIB are the included assertions. These assertions ensure that peripherals are used properly. To enable this, pass DEBUG_EFM to your compiler.

Pin locations

The EFM32 platform supports peripherals to be mapped to different pins (predefined locations). The definitions in periph_conf.h mostly consist of a location number and the actual pins. The actual pins are required to configure the pins via GPIO driver, while the location is used to map the peripheral to these pins.

In other words, these definitions must match. Refer to the data sheet for more information.

Flashing the device

To flash, SEGGER JLink is required.

Flashing is supported by RIOT-OS using the command below:

make flash

To run the GDB debugger, use the command:

make debug

Or, to connect with your own debugger:

make debug-server

Some boards have (limited) support for emulation, which can be started with:

make emulate

Supported Toolchains

For using the Silicon Labs SLWSTK6220A starter kit we strongly recommend the usage of the GNU Tools for ARM Embedded Processors toolchain.

License information

Silicon Labs’ EMLIB: zlib-style license (permits distribution of source).