See LICENSE.md
This material is intended as a companion for the lectures in a course in Embedded Systems. The main objective is to present the inner works of the compilation process and introduce advanced patterns of software for embedded systems.
It assumes a basic knowledge of C. It consists of many small projects, each introducing one, and sometimes two, aspects of the development process.
A companion text describes the projects and the source code. Another text shows how to install the needed tools, how to use them and the structure of a project.
The EFM32 Giant Gecko is a family of Cortex M3 microcontrollers manufactured by Silicon Labs (who bought Energy Micro, the initial manufacturer). The EFM32 microcontroller family has many subfamilies with different Cortex-M architectures and features as shown below.
| Family | Core | Features | Flash (kB) | RAM (kB) |
|---|---|---|---|---|
| Zero Gecko | ARM Cortex-M0+ | 4- 32 | 2-4 | |
| Happy Gecko | ARM Cortex-M0+ | USB | 32- 64 | 4-8 |
| Tiny Gecko | ARM Cortex-M3 | LCD | 4- 32 | 2-4 |
| Gecko | ARM Cortex-M3 | LCD | 16- 128 | 8-16 |
| Jade Gecko | ARM Cortex-M3 | 128-1024 | 32-256 | |
| Leopard Gecko | ARM Cortex-M3 | USB, LCD | 64- 256 | 32 |
| Giant Gecko | ARM Cortex-M3 | USB. LCD | 512-1024 | 128 |
| Giant Gecko S1 | ARM Cortex-M4 | USB, LCD | 2048 | 512 |
| Pearl Gecko | ARM Cortex-M4 | 128-1024 | 32-256 | |
| Wonder Gecko | ARM Cortex-M4 | USB, LCD | 64- 256 | 32 |
The microcontroller used in the STK3700 board is the EMF32GGF1024 microcontroller. Its main features are:
| Device | Description |
|---|---|
| Flash | 1024 KBytes |
| RAM | 128 KBytes |
| Clock | 48 MHz max. |
| VDD | 1.98-3.8 V |
| Power | 10 mA @ 48 MHz, 219 uA @ 1 MHz |
| Package | BGA112 |
| GPIO | 86 pins |
| USB | HS/FS Host Device or OTG |
| DMA | 12 channels |
| EBI | External bus interface 4x256 MB |
| LCD | up to 8 commons and 34 segments |
| USART | 3 |
| UART | 2 |
| LEUART | 2 |
| I2C | 2 (10 Kbps-1 Mpbs) |
| Timer | 4 x 16-bit timer, 4x3 PWM |
| LETIMER | 1 x 16-bit timer |
| ADC | 8 x 12-bit, 500 Ksps |
| DAC | 1 x 12-bit, 500 ksps |
| OpAmp | 3 |
| Comp | 2 x 8 inputs capacitive sensing |
The EMF32GG-STK3700 is a development board featuring a EFM32GG990F1024 MCU (a Giant Gecko microcontroller) with 1 MB Flash memory and 128 kB RAM. It has also the following peripherals:
- 160 segment LCD
- 2 user buttons
- 2 user LEDs
- 1 Touch slider
- Ambient Light Sensor and inductive-capacitive metal sensor
- EFM32 OPAMP footprint
- 32 MB NAND flash
- USB interface for Host/Device/OTG
It has a 20 pin expansion header, breakout pads for easy access to I/O pins, different alternatives for power sources including USB and a 0.03 F Super Capacitor for backup power domain.
For developing, there is an Integrated Segger J-Link USB debugger/emulator with debug out functionality and an Advanced Energy Monitoring system for precise current tracking.
The most important references are:
- EFM32GG Reference Manual[1]: Manual describing all peripherals, memory map.
- EFM32GG-STK3700 Giant Gecko Starter Kit User's Guide[2]: Information about the STK3700 Board.
- EFM32GG990 Datasheet: Technical information about the EMF32GG990F1024 including electrical specifications and pinout.
- EFM32 Microcontroller Family Cortex M3 Reference Manual[4]
There are a lot of peripherals in the board.
- LEDs using pins PE2 and PE3.
- Buttons using pins PB9 and PB10
- LCD Multiplexed 20×8 with a 7 character alphanumeric field, a 4 digit numeric field and other symbols using pins PA0-PA11, PA15,PB0-PB6,PD9-PD12,PE4-PE7.
- Touch Sensor using pins PC8-11.
- Light Sensor using PD6,PC6
- LC Sensor using PB12,PC7
- NAND Flash using PB15, PE8-15, PC1-2, PF8-9, PD13-15
- USB OTG using PF11-12, PF5-6
It is also possible to use the header connectors to add more peripherals.
The EMF32GG-STK3700 board has two USB connectors: One, a Mini USB B Connector, for development and other, a Micro B-Type USB Connector, for the application.
For development, a cable (delivered) must be connected between the Mini USB connector on the board and the A-Type connector on the PC. Among the devices listed by the lsusb command, the following must appear.
Bus 001 Device 019: ID 1366:0101 SEGGER J-Link PLUS
The STK3700 board has two microcontrollers: one, called target, is a EFM32GG990F1024 microcontroller, and the other, called Board Controller, implements an interface for programming and debugging.
For a Cortex M microcontroller the following programming interfaces are used:
- SWD : 2 pinos: SWCLK, SWDIO - Serial Wire Debug.
- JTAG : 4 pinos: TCK, TMS, TDI, TDO - Not used in this board
In the STK3700 only the SWD interface is used, and there is a connector on the SWD lines which permits the debugging of off-board microcontrollers.
Generally, in this kind of boards there is a serial interface between the Target and the Board Controller. It can be implemented using a physical channel with 2 lines or a virtual, using the SWD/JTAG channel. Both appears to the Host PC as a serial virtual port (COMx or /dev/ttyACMx). In the STK3700 board the serial channel uses the UART0 unit (pins PE0 and PE1).
In all examples, a direct access to registers approach was used. It means that no library besides CMSIS was used.
- 01-Blink-Very-Simple: Blink LEDs with direct access to registers
- 02-Blink-Simple-GPIO-HAL-1: Blink LEDs with simple GPIO
- 02-Blink-Simple-GPIO-HAL-2: Blink LEDs with a GPIO module
- 03-Blink-Layered-LED-HAL: Blink LEDs with a LED module over a GPIO module
- 04-Blink-LED-HAL: Blink LEDs with a LED module with direct access to registers
- 05-Using-SysTick: Blink LEDs using SysTick timer
- 06-Changing-Clock-Frequency: Blink LEDs when changing CPU frequency
- 07-Using-a-State-Machine: Blink LEDs using a state machine
- 08-Software-Timers: Blink LEDs using (software) timers
- 09-Button-Polling: Polling buttons
- 10-Button-Interrupt: Buttons generate interrupt
- 11-Implementing-Debounce: Debouncing buttons
- 12-UART-Polling: Simple UART interface using polling
- 13-UART-Interrupt: Advanced UART interface using interrupts and buffers
- 14-Mini-stdio: A simple and small module with some stdio routines
- 15-Using-Newlib: Using the newlib (part of ARM GNU C Compiler)
- 16-Using-a-Time-Triggered-Approach: Using Pont PTTES approach
- 17-Using-a-Better-Time-Triggered-Approach: Using Pont ERES approach
- 18-Using-Protothreads: Using Dunkels protothreads
- 19-Using-FreeRTOS: Using FreeRTOS
- 20-Using-FreeRTOS-with-Interrupts: Using FreeRTOS and interrupts
- 21-Using-uC-OS2: Using uc/OS2
- 22-Using-uC-OS2-with-Interrupts:
- 23-Using-uC-OS3:
- 24-Using-uC-OS3-with-Interrupts:
- 25-Using-the-LCD: Using the onboard LCD (with a simple module)
- 26-Implementing-a-better-Newlib: More advanced implementation of newlib interface
- 27-Getting-Temperature: Showing the temperature from internal sensor
- 28-Software-based-Quadrature-Decoding: Reading the encoder with a state machine
- 29-Hardware-based-Quadrature-Decoding: Reading the encoder using HW timer
- 30-Using-the-Slider-Control: Using the on board slider
- 31-Generating-PWM-Signal: Generating PWM signals using HW timer
- **X32-USB-Device-Barebone: USB interface using a register based API
- **X33-Cleaning X33-USB-Device-TinyUSB: USB interface using a middleware
OBS:
- The hardware decoding in 29-Hardware-based-Quadrature-Decoding is not working well. Probably the encoder is too noisy. I will try with a better one.
- Projects marked with an asterisk are unfinished!!!
- Projects marked with a double asterisk are in a very initial stage