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Silicon Labs SLTB001A starter kit

Support for Silicon Labs SLTB001A starter kit. More...

Detailed Description

Support for Silicon Labs SLTB001A starter kit.


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.



MCU EFR32MG1P132F256GM48
Family ARM Cortex-M4F
Vendor Silicon Labs
Vendor Family EFR32 Mighty Gecko 1P
RAM 31.0 KiB
Flash 256.0 KiB
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
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


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.

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
RTT RTCC 1 Hz interval. Either RTT or RTC (see below)
RTC RTCC 1 Hz interval. Either RTC or RTT (see below)
Timer 0 TIMER0 + TIMER1 TIMER0 is used as prescaler (must be adjacent)
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
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
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.


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).


file  board.h
 Board specific definitions for the SLTB001A starter kit.
file  gpio_params.h
 Board specific configuration of direct mapped GPIOs.
file  periph_conf.h
 Configuration of CPU peripherals for the SLTB001A starter kit.