Introduction to Embedded Programming with ARM Cortex-M3

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1 Introduction to Embedded Programming with ARM Cortex-M3 Alan Xiao, Ph.D Handheld Scientific, Inc.

2 Why ARM ARM is a 32-bit RISC instruction set architecture developed by ARM Holdings. Over 640 processor licenses sold to more than 200 companies Over 17 billion ARM based chips shipped to date ARM chips are used in 99% of the world s cellphones, tablets and other mobile devices. Microsoft announced support of ARM in Windows 8. ARM Techcon conference held every year in Santa Clara Copyright 2011 (c), Alan Xiao 2

3 Latest ARM Family ARM Family ARM Arch ARM-Core ARM9TDMI ARMv4T ARM9TDMI, ARM920T, ARM922T, ARM940T ARM9E ARMv5TE ARM946E-S, ARM966E-S, RM968E-S, ARM966HS ARMv5TEJ ARM926EJ-S XScale ARMv5TE XScale, Bulverde, Monahans ARM11 ARMv6 ARM1136J(F)-S ARMv6T2 ARMv6ZK ARMv6K ARM1156T2(F)-S ARM1176JZ(F)-S ARM11-MPCore Cortex-A ARMv7-A Cortex-A8, Cortex-A9, Cortex-A15 Cortex-R ARMv7-R Cortex-M ARMv6-M Cortex-M0, Cortex-M1 ARMv7-M ARMv7-ME Cortex-M3 Cortex-M4 Copyright 2011 (c), Alan Xiao 3

4 ARM Cortex A Family The Cortex-M Family is primarily for rich OS platforms such as smartphones and tablets ARM Core Features Application Devices Cortex-A8 600MHz 1G Smartphones, tablets, set-top boxes, etc. Apple A4 (iphone, ipad), Freescale imx51, Qualcomm Snapdragon, TI OMAP3 Cortex-A9 Multi-core Apple A5, TI OMap4 Cortex-A15 1-2GHz Multicore Competing with x86 (Intel/AMD) A15 devices will be available Q4/2012 or early Copyright 2011 (c), Alan Xiao 4

5 ARM Cortex-M Family The Cortex-M Family is primarily for low-power micro-controller applications. ARM Core Features Application Devices Cortex-M0 Lowest power, smallest ARM MCU. Clock to 24MHz. Low-end microcontroller NXP LPC11xx Cortex-M1 Developed Specifically for FPGA implementation In FPGA Soft Core for major FPGA: Altera, Xilinx, Actel. Cortex-M3 High Performance MCU. Up to 120MHz Mid to high-end micro-controller NXP LPC17xx, ST Micro STM32 Cortex-M4 DSP Instructions. Memory Protection Unit. Up to 150MHz High-end Computationintensive embedded applications NXP LPC43xx (dual core M4/M0) Copyright 2011 (c), Alan Xiao 5

6 ARM Cortex-M3 Micro-controllers They are micro-controllers Micro-controllers: have everything in them (flash, ram, peripherals, etc.) Micro-processors: usually need supporting chips (memory, peripheral bridges, etc.) From many different companies (NXP/Phillips, TI, Atmel, too many to list. See list in the tool). Use the same core so they are essentially the same in the heart: learn one, use any. Copyright 2011 (c), Alan Xiao 6

7 Cortex-M3 and Operating System What operating systems can they run? No Linux/WinCE/Android (since those normally require MMU). Can run: uc/osii (Micrium), FreeRTOS (freertos.org), ecospro (ecoscentric), CMS (CMX Systems), etc. Carefully consider whether the application needs an OS: Event driven model, SysTick, timer, watchdogs and DMA have powerful OS-like capability OS adds cost and complexity. Hard to debug. If the app really needs an OS, consider ARM9/ARM11. Copyright 2011 (c), Alan Xiao 7

8 Which Cortex-M3? STM32 series from STMicroelectronics Why? Wide range of devices from low-cost (<$2) value line to very powerful STM32F2 (150MHz), all pin and software compatible Software library to ease software development pain (huge advantage) Good selection of development boards Excellent documentation and code examples Supported by all major development tool chains (IAR, Keil, TrueStudio, etc.) Copyright 2011 (c), Alan Xiao 8

11 Software: Which Development Tool? Tier 1: IAR, Keil Tier 2: TrueStudio, Hitex Tier 3: Eclipse, notepad + command line In circuit debuggers/programmers: Segger JLink Keil ULink2 ST Link OpenJTAG, etc. Copyright 2011 (c), Alan Xiao 11

12 IAR Embedded Workbench Trial version (either size limited or time limited) is readily available. For not only ARM but many other chips (8051, TI MSP430, Atmel AVR/AVR32, PIC, etc.) Supports most ARM chips Supports most in-circuit debuggers Fast compilation time Flexibility for advanced users Copyright 2011 (c), Alan Xiao 12

13 STM32 Discovery Kit Value line STM32F100RB MCU, 128KB Flash, 8KB RAM in 64-pin LQFP. 24MHz Clock On-board ST-Link In-circuit debugger/programmer Two LEDs, one user push button and one reset button 32K Real-time clock crystal Extension header for all 64 IOs Powered by USB Very low cost ($12). Perfect for starters. Copyright 2011 (c), Alan Xiao 13

14 STM3210C-EVAL Development Board STM32F107VCT connectivity line MCU, 256K Flash, 64K RAM, 72MHz clock. 3.2 TFT LCD with touch screen. JTAG and Debug Wire connector No ICD but can use the ICD in Discovery kit Relatively costly ($300). Several similar boards from other companies for a lot less (half) Copyright 2011 (c), Alan Xiao 14

15 STM3210C-EVAL Development Board Connectivity features: USB-OTG full speed. USB MicroAB connector. IEEE compliant Ethernet 2 CAN s (Controller Area Network) 5 USARTs, 3 SPIs, 2 IICs. I2S (audio), IrDA, LIN (Local Interconnect network) Other features: Smart card Motor control Copyright 2011 (c), Alan Xiao 15

16 Device Peripheral Library Embedded programming is all about initializing and controlling the peripherals (IOs, USARTs, SPIs, etc.) 32-bit cortex is a lot more powerful and therefore more complex to setup and use The Device Peripheral Library is to shield the complexity from the users. Provides initialization and other major functions Down sides: more typing, larger code size and bugs (rare). Copyright 2011 (c), Alan Xiao 16

17 General Purpose Input/Output (GPIO) Each IO pin can be configured as: Input Analog Input Floating Input pull down Input pull up Output open drain Output pull-push Alternate function open drain Alternate function pull-push Need to specify the max speed of IO, for the purpose of saving energy. Need to turn on the clock of the peripheral Copyright 2011 (c), Alan Xiao 17

19 Example 2: USART (Serial Port) USART/Serial was the most widely used low speed communication protocol before USB Two signal levels: TTL and RS-232 Full duplex with speed up to a few hundreds K bps. Have to specify: Baud rate Protocol (starting bit, stop bit, parity) Use Interrupt. See code. Copyright 2011 (c), Alan Xiao 19

20 USART (con t) TTL/RS232 Level Consideration The USART IO in Discovery board is TTL level. To communicate with a PC: If you would like to use the RS-232 serial port (9 or 25pin D connector) on your PC (assuming there is one), you need a TTL to RS-232 level convertor such as a UT232R-200 from FTDI or a MAX3232 chip. If you would like to use an USB port, you need an USB to USART bridge such as an UB232R module from FTDI. In either case, only 3 wires are needed: Ground, RX<->TX, TX<-> RX. Copyright 2011 (c), Alan Xiao 20

21 What s Next Basics (with the Discovery board): 1. General Input/Output (GPIO) 2. USART (serial) 3. SysTick 4. Unique ID 5. EXTI - External Interrupt 6. Real-time Clock/Calendar 7. Timer/PWM 8. Watchdogs (independent/window) 9. CRC (Cyclic Redundancy Check) 10. PVD (Programmable Voltage Detector) 11. Sleep/Stop/Standby Modes Advanced (with the STM3210C or similar board): 1. I2C/EEPROM 2. ADC 3. RS LCD display/touch Screen 5. SPI and Sensors 6. I2S Audio 7. Wireless (with external 315M and 2.4G modules) 8. USB Mouse and Keyboard 9. USB DFU (device firmware upgrade) 10. USB HID 11. USB Virtual COM Port 12. USB PCM Audio 13. Ethernet Telnet 14. Ethernet HTTP (i.e., control hardware via a web browser!) 15. Ethernet TFTP 16. USB Host 17. Running an OS on Cortex-M3 Copyright 2011 (c), Alan Xiao 21

Embedded Programming with ARM Cortex-M3 Basic Experiments 1

Embedded Programming with ARM Cortex-M3 Basic Experiments 1 Alan Xiao, Ph.D Handheld Scientific, Inc. qiwei@handheldsci.com Today s Topics Basics (with the Discovery board): 1. General Input/Output (GPIO)