Author Archives: R-B

Atmega64 Explorer Board

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Radek Malina from Czech Republic has designed this development board for rapid prototyping and firmware development with Atmel’s powerful Atmega64 microcontroller. He has also shared his design files here. The development board has the following features:

– Atmega64 – all the ports available through pins, a different crystal can be connected (optional frequency crystal)
– DS3231 RTC, real-time IC / I2C
– Temp. DS1820 1wire Temp. sensor
– EEPROM 24AA00SN / I2C EEPROM
– USB Port FT232RL USB/RS232 converter
– Buttons 8x -16x LED
– Connect LCD Display 16×2
– 7segment-LED Display
– N-FET For PWM
– ISP Programming connector

Atmega64 Explorer Board

Atmega64 Explorer Board

Supercapacitors for reliable backup power in embedded systems

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From Samuel Nork’s article “Supercap backup circuit provides reliable uninterrupted power”

Temporary backup power is a common requirement for a wide range of applications whenever the main power source is suddenly unavailable.  Examples include data backup applications ranging from servers to solid-state drives, power fail alarms in industrial or medical applications, and a host of other “dying gasp” functions where orderly power-down must be assured and system status communicated to a powered host.  In the past, these types of high reliability systems used batteries to provide an uninterrupted power source whenever the main supply of power was inadequate or unavailable.

 

 

However, many trade-offs accompany battery backup, including long charge times, limited battery lifetime and cycle life, safety and reliability concerns, and large physical size.  With the advent of high value electric double layer capacitors, better known as supercapacitors, alternate backup architectures may be employed which eliminate many of these trade-offs.

Supercap charger and backup control circuit using

Supercap charger and backup control circuit using LT3350

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MM74C922N-based encoded matrix keypad

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Matrix keypads are an excellent way of providing user input data into microcontroller-based systems. Keypads find applications in remote controls, standalone data-loggers, security systems, door entry systems, calculators, microwave ovens, etc. They are usually implemented as pushbutton switches arranged in a row and column matrix format to reduce the number of I/O connections. For example, a 16-switch keypad is arranged in a 4 X 4 matrix format requiring 8 I/O connections. A pressed key is detected and identified by scanning the keypad to look for a short circuit condition between a row and a column wire. The keypad scanning can be done either by polling or by means of an interrupt routine. In the polling approach, the scanning process is repeated in a continuous loop, which results in waste of CPU time. The interrupt-approach is more efficient and it notifies the processor when there is a keystroke. Another approach of interfacing a keypad to the microcontroller is by using a dedicated keypad encoder IC, which further reduces the I/O connections and makes the interface much simpler. In this project, we are building a simplified 16-switch keypad using the MM74C922 encoder chip, which converts a key switch closure to a 4-bit nibble output.

MM74C22N based encoded keypad

MM74C922N based encoded keypad

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