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Half duplex UART from single AVR pin

Smaller microcontrollers like Attiny84 microcontrollers don’t have UART interfaces, and you may not need them in many cases. But if you want a USART option, you will need to use software USART library or write your own routines. You can find many great software USART libraries for that purpose. As a rule, you will have to use two pins to establish communication. But if you are tight on I/Os, you can cheat a little and make it work from a single pin. Ralph has been experimenting with the simple but intelligent circuit, which allows performing half duplex UART communications with other systems. The whole trick lies in a small schematic made of diode, transistor and resistor. Diode is only for making one way TX signal path from MCU to other device. The resistor is only for limiting base current. All is left a transistor which works as a key. We need to remember that when the serial line is inactive, it stays in the high state. So when microcontroller transmits data, TX on the right keeps transistor open. Thus if…

Configuring the DCO of MSP430

Clocks are an essential part of any microcontroller. These are the first thing one should know while beginning to use any feature of the controller, whether it’s a timer, interrupts, or ADC. All of them rely on the clock setting of the microcontroller and works accordingly. The MSP430 is not so different. However, it features very easy-to-configure clock settings, which might look a bit tough initially, but once you get used to it, you will find it amazing to use. Unlike AVR, where you use super complicated fuse bits to change your clock source and the frequency, this is not the case with the MSP430. The clocks are easily configurable, and most important, if you are using internal clock, you can change its frequency at any time during the program, which is not possible in the AVR series. Before beginning, let me describe our task. We will use a blink-led program, which is already included with CCS and without changing the delay loop, and with the help of the internal oscillator, we will observe a change in blinking time of…

Connecting buttons to MSP430

In this new tutorial, we will see the easiest way to connect a push-button to the MSP430. I will be using msp430 Launchpad for the purpose of the tutorial, however, you can use a bread-board to externally interface the push-button Before I begin, I want to tell you the advantage of Msp430 over other sets of microcontrollers available in the market. As you might have seen, msp430 is a pretty cheap microcontroller from the Texas family, and has a 16-bit wide data bus for processing the data but has very few number of pins. Only 2 ports of 8 pins each are available for interfacing and that two without support for an external crystal. If you want to connect an external crystal, you lose two more pins and that reduces the total number of pins available for interfacing to just 14. But this is just the other side of the coin, the other being its application in low-power projects. Consider a situation where you need to log a data out of a sensor and send it to a local station…

Blinking the LED with MSP430

This is the second tutorial on MSP430, and it will feature code on blinking the led’s and hence will tell you how to configure the ports as input and output and make the port low and high when it’s declared as output. For those having an MSP430 launchpad, it has two onboard led’s connected via two jumpers to pins p1.0 and p1.6. Our task for today is to blink these led’s alternatively or toggle them. To start with an open code composer studio, go to FILE->NEW->CCS PROJECT. After doing this, you will get a window mentioned below Enter your project name, select family as MSP430, and now the variant is msp430g2253. Remember, this is a critical step. To check your option, refer to your chip on the Launchpad. It has a mention of the variant. For all the tutorials, I will be using msp430g2553 as the chip, so kindly change accordingly. In the bottom box, select Empty project (with main.c) and click Finish.

Getting Started With The Msp430

This tutorial is an introductory tutorial on getting started with the MSP430 series of controllers by Texas Instruments. There are millions and trillions of ways to start using microcontrollers. Hobbyist or people who find hard to code typically prefers Arduino as their coding environment, while engineers might prefer using AVR/PIC. The MSP430 microcontroller is a highly versatile platform that supports many applications. With its ability to consume ultra-low power, it enables the designing engineer to meet the goals of many projects. It has, of course, its limitations. It is inclined mostly towards low energy and less intensive applications that operate with batteries, so processing capabilities and memory, among other things, are limited. However, it’s still called a mixed-signal processor and is capable of doing some sort of speech processing. Before starting with some exposure to hardware and software part, I assume that you all have some sort of programming knowledge in embedded c. Even if you know java or c++, you will still be able to adapt to the tutorials easily as the logic will remain the same; only the…

Using Volatile keyword in embedded code

Volatile is probably the least documented keyword in most tutorials and books. This is the primary cause of most misuses and bugs related to it. If you already are programming microcontrollers, you probably know that volatile is always used on global variables that are accessed from interrupt service routines. Otherwise, code won’t work. After few requests, I decided to drop few lines about volatile keywords. This keyword is commonly used to tag memory type. We hear “volatile memory” and “non-volatile memory” when discussing computer hardware. As a quick reminder – “non-volatile memory” is a type of memory that stores its contents even when power is off. Such type of memory is EEPROM, Flash, and FRAM. This is easy from a hardware perspective. But what volatile keyword means in C or C++ code? This is an indicator (called qualifier) to the compiler that tells that this variable may be changed during program flow even if it doesn’t look like it be. This means that compiler must treat this value seriously and keep optimizer away from it.

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