Silicon Labs SLTB001A starter kit

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When using this board with RIOT, set the BOARD variable to sltb001a in your Makefile. If you follow the standard RIOT project structure, your Makefile should look like this:

# name of your application
APPLICATION = hello-world

# Change this to your board if you want to build for a different board
BOARD ?= sltb001a

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

include $(RIOTBASE)/Makefile.include

Support for Silicon Labs SLTB001A starter kit

Overview

Silicon Labs Thunderboard Sense 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	EFR32MG1P132F256GM48
Family	ARM Cortex-M4F
Vendor	Silicon Labs
Vendor Family	EFR32 Mighty Gecko 1P
RAM	31.0 KiB
Flash	256.0 KiB
EEPROM	no
Frequency	up to 38.4 MHz
FPU	yes
MPU	yes
DMA	12 channels
Timers	2x 16-bit + 1x 16-bit (low power)
ADCs	12-bit ADC
UARTs	3x UART, 2x USART, 1x LEUART
SPIs	2x USART
I2Cs	1x
Vcc	1.85 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 pins on the front side of the board. PIN 1 is the top-left contact, marked on the silkscreen.

	PIN	PIN
GND	1	2	VMCU
PA2	3	4	PC6
PA3	5	6	PC7
PF3	7	8	PC8
PF4	9	10	PC9
PF5	11	12	PC0
PF6	13	14	PC1
PC11	15	16	PC10
RES	17	18	5V
RES	19	20	3V3

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

Peripheral mapping

Peripheral	Number	Hardware	Pins	Comments
ADC	0	ADC0	CHAN0: internal temperature	Ports are fixed, 14/16-bit resolution not supported
I2C	0	I2C0	SDA: PC10, CLK: PC11	`I2C_SPEED_LOW` and `I2C_SPEED_HIGH` clock speed deviate
HWCRYPTO	—	—		AES128/AES256, SHA1, SHA256
RTT	—	RTCC		1 Hz interval. Either RTT or RTC (see below)
RTC	—	RTCC		1 Hz interval. Either RTC or RTT (see below)
SPI	0	USART1	MOSI: PC6, MISO: PC7, CLK: PC8
Timer	0	TIMER0 + TIMER1		TIMER0 is used as prescaler (must be adjacent)
	1	LETIMER0
UART	0	USART0	RX: PA1, TX: PA0	Default STDIO output
	1	LEUART0	RX: PD11, TX: PD10	Baud rate limited (see below)

User interface

Peripheral	Mapped to	Pin	Comments
Button	PB0	PD14
	PB1	PD15
LED	LED0	PD11	Red LED
	LED1	PD12	Green LED

Implementation Status

Device	ID	Supported	Comments
MCU	EFR32MG1P	yes	Power modes supported
Low-level driver	ADC	yes
	Flash	yes
	GPIO	yes	Interrupts are shared across pins (see reference manual)
	HW Crypto	yes
	I2C	yes
	PWM	yes
	RTCC	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
Temperature + humidity sensor	Si7021	yes	Silicon Labs Temperature + Humidity sensor
Microphone		no
Pressure + temperature sensor	BMP280	yes	Bosch pressure and temperature sensor
Light sensor	Si1133	no	Silicon Labs UV/Ambient Light sensor
Hall-effect sensor	Si7210	no	Silicon Labs Hall-effect sensor (Rev. A02 boards only)
IMU sensor	ICM-20648	no	InvenSense 6-axis inertial sensor
Air sensor	CCS811	yes	Cambridge CMOS Sensors Air Quality/Gas sensor

Most sensors on this board are controlled via a power and interrupt controller (PIC). By default, this module is enabled. You can disable this module by adding DISABLE_MODULE=silabs_pic to the make command.

Board configuration

Board controller

The starter kit is equipped with a Board Controller. This controller provides a virtual serial port.

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.

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	19 MHz	Enabled during startup, changeable
HFXO	No	38.4 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
LFE	LFRCO, LFXO	Real-time Clock and Calendar

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 32-bit Real-Time Clock and Calendar, which can be configured in ticker mode or calendar mode. Therefore, only one of both peripherals can be enabled at the same time.

Configured at 1 Hz interval, the RTCC will overflow each 136 years.

Hardware crypto

This MCU is equipped with a hardware-accelerated crypto peripheral that can speed up AES128, AES256, SHA1, SHA256 and several other cryptographic computations.

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.

This MCU has extended pin mapping support. Each pin of a peripheral can be connected separately to one of the predefined pins for that peripheral.

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 SLTB001A 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).