Category: AVR Microcontrollers

AVR microcontrollers have EEPROM memory built-in, which adds a lot of abilities to store constant values, calibration data, and other data that may be read and changed at any time during program flow. I have used EEPROM for storing the last device configuration on a couple of projects, e.g., in TDA7313 volume, BASS, TREBLE input, and output channel information is updated each time when it has been changed. After the device is turned ON, it reads the last saved settings from EEPROM memory and restores the last device state. But what happens when you turn the device for the first time. It has to read initial values that have to be stored or read ‘FF,’ which may lead to a crash or something else. One way is to prepare a separate *.eep file with initial EEPROM data and then burn it separately to microcontrollers EEPROM. But this may not always be handy. So this is a simple trick to store initial values to EEPROM at the first microcontroller run and skip this part later without additional files needing to be flashed in. Probably others are doing a bit. Differently, this is how I do. After main() I add following code:…

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Recently I was working on a project where I used a rotary encoder. I could share some thoughts on how the rotary encoder should be interfaced to AVR MCU and write a code to read its value. It is relatively easy to connect and program rotary encoders – only three wires are required to connect to the microcontroller (two for signal quadrature outputs) and one for reference GND). When the encoder knob is turned in either direction, it generates a Grey code on the outputs, allowing tracking turn speed and direction. Rotary encoder allows including a convenient user interface option with a single knob. Many rotary encoders also come with an integrated button on the knob itself – so menu navigation becomes even more comfortable. In our example project, we are going to use a 12-step mechanical rotary encoder from SparkFun. It is interfaced to ATMega32 board with graphical LCD.

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Timers are an essential part of embedded systems. They make your life much more comfortable if used properly. Timers run independently to main program flow, so they can do job individually without disturbing precious calculations done by CPU. You just set up the timer and let it run while your main program performs other tasks. Timers are easy to set up. In this post, an example is made for Atmega8 timers. Other AVR microcontroller models and even different brand chips have similar timers. Atmega8 has two 8 bit timers/counters and one 16-bit timer counter with many abilities. Standard 8-bit Timer/Counter0 features are: Single channel counter; Frequency generator; External Event counter; 10 – bit clock prescaler. TCNT0 is an 8-bit timer counter register which keeps the current count number. Timer counter can be clocked by an external clock through pin T0 or from internal via pre-scaler. Timer counter is incrementing (MAX value is 0xFF) and then restarts from BOTTOM=0x00. After timer Overflows, the flag TOV0 is written to 1, and if TOIE0 bit in SREG is set, and then timer overflow interrupt is executed. TOV0 acts as a ninth bit of counter register that is only set but not cleared. When…

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Simple USART routines are not always practical because waiting transmitting buffer to be ready in a simple loop occupies processor resources. If we do not know when data will be received, we are just wasting resources inside waiting loop. Another issue arises when multiple data bytes has to be sent/received. In this case, we have to write complex code to deal with data flow. Since microcontroller speciality are interrupts, it is better to use them to handle communications and this way improve overall performance and energy saving. Instead, of continuously checking if there new data received in the UDR register or checking if send buffer is free, lets us write more effective USAR communication code with a guardian which would wake the MCU if it have received a byte via USART. In other hand, Interrupt mode allows to perform other tasks at full capacity while waiting for USART interrupt. Let us implement interrupt driven AVR USART communication example. For this we will need to include the interrupt library: Then we will have to enable USART Receive Complete Interrupt (USART_RXC_vect) and enable global interrupts. Then write interrupt service routine ISR(USART_RXC_vect). Let us write simple bounce program – USART sends back incremented…

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