I2C EPROM programmer

Sometimes you need to program I2C EEPROM chips and don want to invest any bucks in it. Then you should consider the I2C EPROM programmer originally designed by Claudio Lanconelli. This is very easy to build and use circuit but it supports 24C01, 24C02, 24C04, 24C08, 24C16 24C32, 24C64, 24C65, 24C128, 24C256, 24C512 I²C Bus EEPROM, auto-detects 24XX EEPROM capacity For the I2C EPROM programmer, you need to download PonyProg programmer software from www.lancos.com. Choose “Easy I2CBus” from the Options – Setup menu and the parallel checkbox on WindowsNT/2000. You have to select “AVR ISP I/O.”

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Serial Peripheral Interface – SPI Bus overview

Serial Peripheral Interface is a simple interface that enables communicating microcontroller and peripheral chips or intercommunicating between two or more microcontrollers. Serial Peripheral Interface Bus, sometimes called four-wire interface, may be used to interface such chips or devices like LCD, sensors, memories, ADC, RTC. The range of usage is huge. SPI Bus uses the synchronous protocol, where transmitting and receiving is guided by a clock signal generated by the master microcontroller. SPI interface allows connecting several SPI devices while master selects each of them with CS (Chip Select) signal – (Underline means that active is LOW). SPI bus consists of four signal wires: Master Out Slave In (MOSI), Master In Slave Out (MISO), Serial Clock (SCLK or SCK) Chip Select (CS) for the peripheral. Some microcontrollers have a dedicated chip select for SPI interfacing called Slave Select (SS). The master generates a MOSI signal – the recipient is Slave. MOSI may also be labeled as SI or SDI. Slaves generate MISO signals. In some chips, you might find labels SO or SDO. SCLK or SCK are generated by master to synchronize data transfers. CS (SS) signal is also generated by master to select slave chip or device. Data transfer is…

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7805 voltage regulator for your design

This is the most common voltage regulator that is still used in embedded designs. The LM7805 voltage regulator is a linear regulator made by several manufacturers like Fairchild or ST Microelectronics. They can come in several types of packages. For output current up to 1A, there may be two types of packages: TO-220 (vertical) and D-PAK (horizontal). With a proper heat sink, these LM78xx types can handle even more than 1A current. They also have Thermal overload protection, Short circuit protection.

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Using VMLAB as virtual oscilloscope

VMLAB is one of the well-known simulators. This is a software simulator of AVR and ST62 microcontrollers. The simulation is far away from real-time, but All timings are tied to real-world values. VMLAB is designed to work as a project. This is a special language (script like), where the circuit is described – where are connections between hardware and microcontroller defined. You may find few prebuilt examples in folders C:\VMLAB\AVR_demo and C:\VMLAB\ WinAVRdemo (If your installation is in C:\VMLAB\ folder). VMLAB is rich in its hardware support: Resistor, Grounded capacitor, Interactive switch/key, LED, Pulsed voltage source, Sine wave voltage source, Slider dependent voltage source (interactive), Non-return-to-zero (NRZ) generator (interactive), Operational amplifier, Comparator, 2 inputs NAND gate, 8 bits D to A converter, RS232 based TTY (interactive), LCD module, I2C monitor (interactive), Interactive keypad 4×4 Multiprocess-dedicated: External Input, External Output. So you can do a wide range of simulations. VMLAB also has a powerful scope where you can watch voltages on pins or even some internal microcontroller resistor values like ACO, TIMOVF signals. Let’s make simple project using VMLAB tool. Start VMLAB And create new project by selecting Project-New. Select project properties like project location, c file name, microcontroller type, software…

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Frequency response of discrete system

In the previous post, we discussed the impulse response. Impulse response h(n) is a digital system response in the time domain. But there is another characterization of the discrete system – frequency response H(ejω). Frequency response can be calculated form impulse response by formula: This means frequency response is the systems transfer coefficient to every frequency value. Frequency response is a complex function. So this can be evaluated as:

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Digital system equation

Back to the DSP thread. Let’s talk about the digital system equation. Every digital system can be described using this equation. The output of the digital filter generally consists of previous inputs and previous outputs. y(n-k) is considered as previous outputs; x(n-p) – previous inputs; ak and b­p – coefficients; This equation is convenient to define the discrete systems and extract various characteristics. Number N defines a discrete filter tap (Tap – A FIR “tap” is simply a coefficient/delay pair). Lets say we have digital filter made of one tap. y(n)=a·y(n-1)+b·x(n) First we calculate filter response function – h(n): Response function is calculated from system reaction to discrete impulse ´(n). So assume that x(n)= ´(n) and y(n)=h(n). Initial conditions: y(-1)=h(-1)=0. Then: h(n)=0 when n<0; h(0)=a·h(-1)+b·´(n)=b; h(1)=a·h(0)+b·´(1)=ab; ……. h(n)= ban where n>0 Lets say we have a=0.7; b=1; Then we get discrete system characteristics: This equation in example describes IIR (Infinite Impulse Response) discrete systems because there is a feedback element a·y(n-1). There is another type of discrete filter – FIR (Finite Impulse Response) Finite response filter equation is much simpler: As you may notice from the equation – the IIR filter has an infinite number of response impulses while the…

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AVR microcontroller interrupts using WINAVR

I can’t imagine a microcontroller without interruptions. Without interrupts, you would have to make loops to check if one or another event occurred. Polling has many disadvantages like programs have to make loops, which takes valuable microcontroller resources. These resources may be used for other data processing tasks. This is why the microcontroller comes with built-in interrupt support. Instead of checking events, the microcontroller can interrupt normal program flow and jump to interrupt the service subroutine. During an interrupt, the microcontroller stops the task at the current point, saves necessary information to stack, and gives resources to interrupt the subroutine. When interrupt subroutine finishes, and then normal program flow continues. In assembler your program would start with interrupt table: After the table goes the main program (RESET) and other interrupt subroutines where the program jumps after the interrupt occurs.

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ADC on AVR using on chip comparator

Not all AVR microcontrollers come with built-in ADC. But there is a way of building one using an on-chip comparator and timer counter. The comparator compares voltages on +v (Ain0) and -v (Ain1) inputs. If the Ain0 pin’s voltage is greater than in Ain1, then the comparator ACO is set to ‘1’ otherwise, it is ‘0’. Bellow you see AVR comparator circuit. The working of this ADC is as follows. First, PB0 is set to ‘0’ to discharge the capacitor. Then PB0 is programmed as input with no pull-ups, and Timer is started to count.

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Understanding Timing diagrams of digital systems

Timing diagrams are the main key in understanding digital systems. Timing diagrams explain digital circuitry functioning during time flow. Timing diagrams help to understand how digital circuits or sub-circuits should work or fit into a larger circuit system. So learning how to read Timing diagrams may increase your work with digital systems and integrate them. Bellow is a list o most commonly used timing diagram fragments: Low level to supply voltage:

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