June 2007 - Do It Easy With ScienceProg

Chemical effects of electricity

Electronics depend on chemistry more than you can imagine. To generate electricity, there are many methods used; one of them is chemical. Remember batteries, where electricity is generated because of chemical reactions inside the cell. In conductors like liquids and gases, electricity is carried not by electrons in solid constructions(copper, aluminum, etc.) but by ions – molecules with electric charges. Even non-distilled water contains enough ions to be conductive. Let’s go through several chemical effects of electricity. Electrolysis Electrolysis decomposes the liquid compound by passing an electric current through a liquid called an electrolyte(saltwater, copper sulfate, sulphuric acid). Electrolysis is used very widely in the industry, like electroplating metals, refining copper, and extraction of aluminum from ore. To make electrolysis happen, two conductors used cathode(-) and anode(-).

Circular buffers in DSP processors

I will not analyze what DSP processors are different from regular microcontrollers as many differences allow boosting performance in many specific tasks like filtering, FFT, etc. One thing is obvious that DSP processors have to perform mathematical calculations rapidly enough to get predictive results. The better result we want – the more processing power we need. We know that MCU is performing two main tasks: data manipulation and mathematical operations. But the fact is that it has to be done really fast. General-purpose microcontrollers aren’t optimized to perform these tasks effectively as microcontroller has to as much universal as possible to fit in many areas. In other words, flexibility reduces performance. DSP processors are more specialized microprocessors optimized for tas that they usually do – multiplication and addition. Let’s take the most common DSP routine FIR digital filter implementation. It takes several samples of signal x[] and produces output signal y[], modified by multiplying appropriate samples by coefficients an. y[n] = a0x[n]+a1x[n-1]+…+akx[n-k]

Automated electronic CAD systems overview

More and more design operations become automated. These changes give many benefits like effectiveness, minimal errors, and less routine operations to designers. Modern electronic equipment requires scrupulous planning as devices shrink to minimal sizes, operation power increases, and it fit its external design requirement. So designing is a very complex task where without smart CAD software would be almost impossible to do. When designing a new electronic device, you have to deal with several necessary areas to make the device a reliable and attractive device. All of these areas usually are done on a particular CAD system. The most common CAD-based electronic specific task are: Mixed Analog-digital device modeling; Programmable Logic modeling and synthesis; HF circuits and electromagnetic modeling; Functional modeling; PCB Design; Thermal modeling; Chip topology modeling. Each of these modeling and designing processes requires different skills and knowledge. Let’s go through each to see their specifics and what CAD systems are used to automate related tasks.

AVR analog comparator and avr-gcc example

An Analog comparator is a pretty simple peripheral, but it can give big benefits. Comparator module is included in all Mega series of AVR microcontrollers. Simply speaking, Comparator allows comparing voltage values applied to two pins of microcontrollers. The comparison results are a logical level, which can be read by the program(ACO- Analog Comparator Output bit). There is also the ability to generate an interrupt, which depends on the comparator resulting level. And more- timer T1 can capture this level what allows measuring the signal length of analog signals. To use pins as comparator inputs, they must be prepared and configured as input(DDRx=0), and pull-up resistors must be disconnected (PORTx=0). In some models like Atmega48x/88x/168x, Atmega165x, Atmega325x,3250x,645x/6450x, and Atmega640x/128x/1281x/2560x/2561x, there is the ability to disconnect digital buffers of AIN0 and AIN1 pins that allows the use of these pins only for analog signal input – this minimizes overall power consumption.

JTAG wiggler clone for ARM microcontrollers

The Olimex ARM JTAG clone is well known as there are many schematics on the internet available. Circuits are straightforward and seem to be reliable. This adapter can also be set up to work with WinARM tools: obdremote and gdb/Insight-gdb. In the circuit, there is a critical part that needs to be considered – 74HC244 buffer IC. Family of HC support less than 4.8V if powered with 3.3V. But reality shows that Parallel port voltage usually is lower than 5V so that HC will fit. But of course, it is better to measure the HIGH state of parallel port pins. To be more sure, HC should be replaced by 74LVP244 or 74LPT244. These chips support 5.5V in entry with a 3.3V supply, but sometimes they are hard to find in the market.

What is DebugWire interface

Debug wire is an interface that enables debugging AVR microcontrollers by using one wire. All new AVR microcontrollers with less than 16kByte memory have a built-in one-wire bidirectional debugging interface that allows debugging devices in real-time. Like the JTAG interface, DebugWIRE can handle full execution and program flow control. It also supports an unlimited number of breakpoints, adjusting memory contents. The good thing is that interface doesn’t require additional pins as only the RESET pin is used for debugging purposes.

Major programmer types for 8 bit AVR microcontrollers

AVR microcontrollers have many ways to be programmed. One type of adapters are used only to program AVR memory others are used to program and debug. AVRISP The most known and common programming adapter is AVRISP, which is the basic tool and can be used to program Flash, EEPROM memory, most of the fuses, lock-bits for probably all 8bit AVR MCU’s. The programmer connects to a computer via an RS232 serial interface powered from the target board with no need additional power supply. The programmer connects to the target board via one of two headers â€“ 6 or 10pin. AVRISP from Atmel Corporation is designed to work from AVRStudio as front end software and is upgradable. However, AVRISP is discontinued due to the newer adapter appearance – AVRISP MKII. There are cheap third party clones available. But most of them aren’t compatible with AVRStudio but work well with programs like PonyProg or AVRDUDE.