R-B | Embedded Lab

Author Archives: R-B

Lab 17: Sleep and Wake PIC microcontrollers

Posted on August 6, 2011 by R-B 32 comments

PIC microcontrollers’ Sleep feature is an extremely useful mechanism to minimize power consumption in battery-powered applications. In Sleep mode, the normal operation of a PIC microcontroller is suspended and the clock oscillator is switched off. The power consumption is lowest in this state. The device can be woken up by an external reset, a watch-dog timer reset, an interrupt on INT0 pin, or port-on-change interrupt. In this experiment, we will discuss how to put a PIC microcontroller into Sleep mode and compare the current consumption during Sleep mode and the normal operation mode.

Understanding Sleep mode

In-Circuit Debugging of PIC microcontrollers

Posted on July 31, 2011 by R-B 6 comments

An In-Circuit Debugger (ICD) is a very powerful and effective tool for real-time debugging of a microcontroller-based system at hardware level. It allows you to run, halt and single step the program while the target microcontroller is embedded in the actual circuit. Once halted, the program variables, Special Function Registers (SFRs), RAM and EEPROM locations can be examined and modified in real-time, thus assists the designer in debugging the firmware and hardware together. In this article, I am going to describe the In-Circuit Debugging technique in PIC microcontrollers, and demonstrate the debugging procedure with a test project using the PIC16F887 microcontroller. Although the operation of most ICDs are similar, here I will be using mikroElektronika’s PICFlash with mikroICD device in conjunction with the mikroC Pro for PIC compiler for illustrative purpose.

Use of ICD in debugging PIC programming

Atmega8 measures ambient temperature and relative humidity using HSM-20G sensor

Posted on July 22, 2011 by R-B 7 comments

In one of my previous posts, I discussed about Sensirion’s SHT11 and SHT75 sensors, which are capable of measuring both temperature and relative humidity. They are digital sensors and provide fully calibrated digital outputs for temperature and relative humidity. I also illustrated how to interface those sensors with a PIC microcontroller. Shawon Shahryiar from Dhaka, Bangladesh shared this project with us where he describes a method of interfacing the HSM-20G sensor to Atmega8 for measuring the ambient temperature and relative humidity. Unlike Sensirion’s SHT series, this is an analog sensor that converts the two ambient parameters into standard output voltages.

Using HSM-20G sensor with Atmega8

Lab 16: Understanding Interrupts

Posted on July 21, 2011 by R-B 12 comments

Interrupts are powerful concept in embedded systems for controlling events in a time-critical environment. In a typical embedded system, the embedded processor (microcontroller) is responsible for doing more than one task (but can do only one at a time). For example, let’s say in a programmable digital room thermostat, the microcontroller is assigned to monitor the room temperature, turn the AC or heater ON and OFF, control the LCD display, and respond to any new temperature setting from the user. Out of these the first three tasks are non-time-critical and are executed continuously in sequence one after the other, within the main loop. But when the user presses any button on the setting panel, the microcontroller should be able to read it before the user releases the button. So this is a time-critical event and the microcontroller should stop whatever it is doing and respond to this higher priority event. This is possible through the use of interrupts. This tutorial first describes the interrupt system in general and then illustrates how it is handled in PIC micrcontrollers.

Understanding interrupts in PIC microcontrollers

Using TC74 (Microchip) thermal sensor for temperature measurement

Posted on July 17, 2011 by R-B 26 comments

The TC74 chip is a serially accessible, digital temperature sensor from Microchip Technology that acquires and converts temperature information from its onboard solid-state sensor with a resolution of 1°C. The temperature is available as an 8-bit digital word stored in its internal temperature register, which is accessible through a 2-wire I2C compatible serial bus. This tutorial describes how to use the TC74 sensor with a PIC microcontroller to measure the surrounding temperature.

Using TC74 sensor for temperature measurement

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