Testing Your Embedded System

Every time you are making some circuit or more complex system, you always do some testing to make sure that your electronic “baby” is working properly and you can expose it to publicity. Lets say you are constructing some kind of robot. Then typical list of testing task may be as follows: Stability tests using various working modes and critical supply voltages (like 4,75 and 5,25V); Start up testing – purpose is to check system readiness to accept commands after power up; Checking correctness of executed commands; Checking correctness of sensors; sometimes you will need to prepare good documentation where every node reliability is calculated. Also testing methods of each nodes may be included in documentation. Of course many devices may work in wider range of supply voltages, but there are always some electronic components that needs more than 5% stability. If your system is bigger and may be dangerous…

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Choose right electronic components for your projects

Every time you start your project one of the most important things is to thinking about what electronic components you will choose. There might be a series of questions you might have to answer for yourself. Lets say you will construct some robotic or other sensor related system based on microcontroller. Then questions might be as follows: What type of microcontroller to use for your project? What type of clock generator to use? What type of power source to use? What type of sensors will be used for gathering of information? What will be output devices (motors, displays)? Will you need some kind of memory excluding internal microcontroller memory? Can all required components be found without problems? And the last question you will need to ask yourself is: Can other amateurs repeat your project on your component base? Lets say you will make your system using some exotic electronic components…

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Microcontroller Brown-out detection

Mostly all microcontrollers have built in Brown-out detection (BOD) circuit, which monitors supply voltage level during operation. BOD circuit is nothing more than comparator, which compares supply voltage to a fixed trigger level. If microcontroller doesn’t have On-Chip Brown-Out detector, then there can be external circuit used : The circuit above illustrates the brown out detectors circuit. In real word there are special IC where additional delay circuitry and hysteresis used because normalizing of supply voltage may take some time. Such IC’s are more cheap than one built from discrete components. As an example lets take Atmega128 microcontroller which have On-chip Brown-Out detector. Trigger level can be 2,7V or 4,0V (selected by programming Fuse bits). Trigger level also has a hysteresis to avoid spikes. The hysteresis can be interpreted as VBOT+=VBOT+VHYST/2 and VBOT-=VBOT-VHYST/2. So if Brown-Out circuit is enabled by the Fuse bit and Vcc voltage decreases to a value…

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Modifying the Scanner for Watermark Scanning

The guy so called bunnie made interesting project by modifying the flat scanner. He managed to enhance watermarks by using blue LED’s instead white ones. He built a bar of of surface mount LED’s and placed it instead of white led bar. Using such scanner watermarks become visible to the naked eye. Read more at www.bunniestudios.com

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Radio Frequency Identification RFID

There are two types of RFID devices: Active and Passive. Active devices have power source built in which supplies the transmitter. The transmitter is triggered by sending the signal to RFID device. These devices have their own code and can transmit signal in desired time intervals. Active RFID devices are good in defining locations of objects or sending some information about particular place (RFID-based location determination). Active RFID devices use high frequencies (455MHz, 2,45GHz or 5,8GHz) – working range about 20 – 100 meters. The most common are passive RFID. They don’t need power source. Passive RFID devices are low frequency(124 – 135kHz – low) and high(13,56MHz – 960KHz – high; 2,45GHz – UHF). The working principal of low and high frequency devices differ. While low frequency readers generates magnetic field which induces current in RFID device antenna. The chip inside RFID device modifies this magnetic field which is read…

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What is surface mounting

Simply talking surface mounting is a soldering technology where component is soldered directly to a series of solder pads called a footprint. It is different soldering technology from through hole, where component leads are inserted into holes of the board. Footprint is a series of pads that conform to the lead layout of packages of surface mount devices (SMD). Surface mounting has several advantages over through hole technology. First of all the board become much smaller. So smaller boards and more dense placement of elements reduce costs. Because of higher placement density traces between components becomes shorter. It lowers parasitic inductance and capacitance. Table shows the changes while redesigning the through hole board to SMT. We can see the board size were reduced by 59%, the number of layers was reduced from 6 to 4 and the costs were cut in half. Now everyday new components are introduced. Probably there…

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Control memory sections using AVR GCC

If you programming AVR microcontrollers in C usually you don’t think how compiled program is stored in microcontrollers flash memory. Compiler organises data in the way it looks optimal. But sometimes you are working with programs where you need you code chunks located in specific program memory locations. For instance faced this problem while developing an AVR controlled signal generator. I wanted to make efficient and compiler independent main loop where the signal has to be read from flash memory and transferred to port. I managed to use in line ASM function which does the job: //…………………………………………………….. void static inline signalOUT(const uint8_t *signal, uint8_t ad2, uint8_t ad1, uint8_t ad0) { asm volatile( “eor r18, r18 ;r18

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