Challenges in Embedded Development

M. Kaisar Ul Haque Principal Software Engineer ReliSource Technologies Ltd.

The Embedded Platform 8 bit MCU (Microcontroller Unit) 16 bit MCU 32 bit MCU/Processor Costing, Physical Size, Power Consumption, Computational Power, Resources (RAM, Program memory, Peripherals). All architectures are currently popular, for example new 8 bit models comes out every few months!

Resource Constrains 8 bit MCU, an example: 1 KB of RAM 16 K instructions / Code Size / Program memory Limited peripherals

Resource Constrains (Contd.) “ What makes ESW different [from other software development] is resource constraints,” says Bob Iannucci, senior vice president and head of Nokia Research Center, Nokia's corporate research unit in Helsinki. Dr. Zhang agrees: “You have to think about space, power conservation and pixel constraints. You have to balance power, simplicity, footprint, cost and size.”

Code Size long SomeFunction(long a, long b) { long c = a * b; return c; }

Code Size (Contd.) long SomeFunction( long a, long b) { long c = a * b; return c; } Assignments can be expensive!

Code Size (Contd.) uint16 SomeFunction( uint8 a, uint8 b) { uint16 c = a * b; return c; }

Code Size uint16 SomeFunction( uint8 a, uint8 b) { uint16 c = a * b; return c; } Function calls can be expensive! Next instruction (PC) is changed, Stack frame is changed Parameters are placed in stack (assignments) Room made for return value Room made for locals Function code executes Return value stored (assigned) Stack frame changed / popped Return value assigned as function’s value PC is changed / popped

Code Size (Contd.) Macros are better in many cases But not in all cases.. #define SomeFunction(a, b) ((a) * (b)) x = SomeFunction(y, z);

Code Size (Contd.) Multiplications can be expensive.. x = y * 8; x = y << 3; Floating point operation can be expansive 1.5 * 1.5 = 2.25 is more expansive than 15 * 15 = 225

Code Size (Contd.) What machine code/instructions your code generates How to minimize your code Save every instruction you can Hundreds of business logics can be difficult to fit into the program memory (for example in 16k)

RAM Size How much RAM your code needs? How to minimize RAM utilization? Save every ‘bit’ you can.. Literally

RAM Size (Contd.) Many data types (int, long, float, double) can be expensive! long SomeFunction( long a, long b) { long c = a * b; return c; }

RAM – Saving every ‘bit’ uint8 a; //value range 1 to 50 uint8 b; //value range 1 to 10

RAM – Saving every ‘bit’ uint8 a; //value range 1 to 50 uint8 b; //value range 1 to 10 typedef struct { uint8 a: 6; uint8 b: 2; } s_ab; s_ab ab; //takes 1 byte

Power Sleeping is better than working :) Some peripherals consume more power High clock speed consumes more power Need to save as much uA as possible Less utilization of power = more battery life = less cost = better business = less batteries = greener world

Real-time Issues Some communication timing must be precise.. Depended on the clock.. the clock doesn’t run at the speed it should.. You asked for 2 MHz.. you got 1.4 MHz.. 26uS

Expertise over ‘the Platform’ Memory – Banks, Addressing Peripherals – Clock, WDT, IRQ, IO, LCD, ADC, RTC, TBC, Timers Communications - UART, I2C, SPI Spec/Datasheet, User Manual, Instruction set, C Language, Compiler, Assembler, Linker Docs

Cross-Platform Architecture Codes needs to support current and future target platforms Hardware abstraction layer is required to separate platform specific and business codes. Reusable modules is the key Changes in a module needs to be tested over all platforms

Shortage of Documents Not much example code from vendor No example/help returned in Google Platform not yet released in the market You only have the documents provided by the MCU vendor and those can have errors!

Debugging Limited support of break points Many real-time scenarios are impossible to debug Need the right tools to debug

Collaboration “ Any device we manufacture these days is getting more and more complicated, with quite a bit of software and hardware integration,” says Woo-hyun Paik, president and chief technology advisor at LG Electronics in the United States. “You can't do it all by yourself.”

Testing, Testing.. Testing Accenture’s AJ Gupta. “Without a structured approach to testing, a company cannot effectively match initial product requirements with specific testing activities and expected actual outcomes. This—coupled with the fact that many companies lack the robust tools necessary to adequately test today’s complex high-tech products— results in bugs that go uncaught before the product is shipped.”

Challenges in Embedded Development

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