Projects, tutorials, and articles about microcontrollers (AVR, PIC, 8051, MSP430, and STM32 or other ARM architectures), FPGA, analog electronics, and digital electronics
Humidity sensors measure the relative humidity of air. They come in different types – both digital and analog types. The digital types are relatively more expensive than the analog types. The measured relative humidity by digital humidity sensors are commonly sent out using digital serial interfaces like I2C and SPI. Analog humidity sensors are cheaper and they come in two types – capacitive and resistive humidity sensors.
In this tutorial, I am going to show how to use AVR Studio IDE and WinAVR in developing software for AVR microcontrollers. In this tutorial, my target AVR microcontroller is ATmega8 and I will be using AVR Studio version 4.18.700. I am assuming that you have downloaded and installed WinAVR and AVR Studio. If you have not installed both, please do so. Installation must be straight forward and please use the default installation directories to avoid confusions.
If you have already installed AVR Studio and WinAVR, then you are ready to get started with the software development.
1. Run AVR Studio by double-clicking the AVR Studio icon on your desktop or by going to Start->Programs->Atmel AVR Tools->AVR Studio 4.
Good day! Today, I am starting a new series of microcontroller programming tutorials. This series of tutorials is about AVR microcontroller programming using C language.
Before we get started, let me express my assumptions while writing this series of tutorials. In this series of tutorials, I am assuming that the reader is already familiar with C programming language. I am assuming that the reader knows how to read a schematic diagram, construct a circuit based from a given schematic diagram, and analyze electronic circuits. I am also assuming that the reader is able to use Windows applications. [Read more...]
An interrupt is an asynchronous signal that needs attention. An interrupt stops the CPU of a microcontroller, leaving the tasks that it is currently doing, to give attention to the interrupt signal. Once the attention has been given to the interrupt signal, the CPU goes back to its unaccomplished task before the interrupt has occured and continues the task.
The interrupts of AT89C2051 is compatible with the interrupts of the original 8051 microcontroller. It has 6 interrupts sources ( 5 interrupts + RESET). The interrupt sources of AT89C2051 are the following:
| Interrupt | Source | Priority Number | |
| 1 | RESET | RST | N/A |
| 2 | External Interrupt 0 | IE0 | 0 |
| 3 | Timer 0 Interrupt | TF0 | 1 |
| 4 | External Interrupt 1 | IE1 | 2 |
| 5 | Timer 1 Interrupt | TF1 | 3 |
| 6 | UART Interrupt | RI or TI | 4 |
Please note that in this tutorial, we will not consider the interrupt from RESET.
The table above shows the interrupt sources of AT89C2051 and their respective interrupt priority number. Knowing the priority number is important specially if two different interrupt sources occur at the same time. [Read more...]
UART stands for Universal Asynchronous Receiver/Transmitter. As its name implies, it is universal. It can be used to establish a communication between a microcontroller and another device – microcontroller, USB controller, Bluetooth modules, GSM modules, GPS modules, personal computers, etc.
I am not going to discuss the UART protocol here. If UART is still unknown to you, you may read this article from wikipedia first.
RS-232 is a standard for serial transmission of data between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly found in desktop computers where it is commonly referred as COM port. You can read this wikipedia article for more info about the RS-232 standard.
The AT89C2051 has one UART port. Its TXD (Transmit) pin is the same as its P3.1 pin. Its RXD (Receive) pin is the same as its P3.0 pin.
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