In more complex projects where audio or video are involved, microcontrollers usually run out of internal RAM. The only solution that stands out is adding external RAM. Depending on platform and solution used there are many ways of doing this. But usually goes SRAM modules, latch register(s) and probably some other additional circuits. If you only need to add more RAM without planning all this you can use RAM module like this one made by [Wardy]. This is simple RAM module with 512Kbytes of static RAM. It only needs 13 pins for interfacing and can accept voltage levels 3.3V or 5V. PCB layout is designed so that pins are breadboard compatible – easy to play with any microcontroller or dev board like Arduino.
AVR microcontrollers aren’t the best choice to run FreeRTOS scheduler due to low on-chip RAM. Atmega128 has only 4K of RAM, so this limits the FreeRTOS functionality to very basic. Anyway, this problem can be solved by adding extra RAM which may be connected to an external memory interface. We have already built an external memory block of 8K previously so now we can test it with FreeRTOS applications. Lets continue with our previous code which runs several simple tasks (button state reading, LCD output and LED flash), and we can add more to it. We are going to set up an external RAM for storing heaps. This will allow to store large data buffers without worrying too much about heap and stack overlaps.
Modern cars have more electronics than you can think. Almost every vital part has tons of sensors on it that has a dedicated computer called ECU (Electrical Control Unit). Usually, there are from several up to hundreds of ECU’s on a single car. Especially luxury ones. All modules have to work as an organized unit. So this is where reliable connection interface needed. Probably you’ve already heard of CAN bus (Controller Area Network). It is a standard bus interface used in most vehicles where board computer communicates with separate control ECUs taking care of engine, gearbox, climate, security alarm, safety bags. CAN devices are connected by using twisted pair signal wires that are more resistant to noises. Signals usually operate at the 5V level. The transfer speed can reach up to 1Mb/s for 40m cable lengths. Engineers have put lots of thought into CAN protocol. It was designed to be flexible, reliable, and robust. There can be more than one master CAN device on the same bus. For instance, there can be a situation when several masters start communication at the same time. In this case, there is a message priority used to determine which one will have the right…
Over a week ago I’ve got a notice that Texas Instruments (TI) is giving away a 50% coupon for MSP430_FRAM related devices. Without hesitation ordered their MSP-EXP430FR5739 TI experimenters board that price went down to $14.50 including free shipping. With all functionality and on board peripherals included – its a give away. Experimenters board came in nice hard paper package that feels really solid and professional in hands.
There are many projects where you may need to measure currents. The problem is that basically microcontrollers are equipped with ADC that are used to measure voltage levels. In order to measure current you need somehow to convert current to voltage. The simplest way is to pass this current through resistor with small resistance and measure voltage drop across it. Then you can measure voltage drop across this known resistor with microcontroller ADC and then apply simple Ohm’s law to find current. Follow this reading to find out how to expand drop voltage dynamic range so microcontroller could read it with maximum accuracy.
Microcontrollers are the building blocks of any digital signal processing system. In layman’s terms, they can be described as miniature computers that are present on chips. They consume very little amount of power and are self sufficient. They are similar to microprocessors but contain some additional elements such as read only memory in the form of EEPROM (Electrical Programmable Read Only Memory) and a read write memory that usually utilises flash technology.
Space exploration isn’t an easy task, as it requires many high-end technology to keep all the devices functioning well in extreme temperatures and the risk of exposure to radiation. An Electrical engineering researchers from University of Arkansas have successfully designed and tested an electronic micro amplifier, where it claimed can operate normally in the space environment without protection from a warm box. This superb electronic amplifier is capable of performing with consistency and stability at extreme temperatures, where it ranges from 125 degrees Celsius to negative 180 degrees Celsius. Furthermore, it saves power and space that required for electronic circuitry. Alan Mantooth, professor of electrical engineering and holder of the Twenty-First Century Endowed Chair in Mixed-Signal IC Design and CAD, explained that the device is the first fully differential amplifier circuit, where it’s mainly designed specifically for extreme temperatures, including temperatures in the cryogenic region. This electronic amplifier has a power supply of 3.3 volts. It uses two common-mode feedback circuits to control the voltage of both the input and output stages. The researchers are continuing to construct an amplifier, where is provides a larger differential gain across both wide frequency and temperature. So, please wait and see by yourself…