![]() ![]() We are going to continuously transmit an ASCII string "Hello from ATmega328p" to the PC. Enabling RXEN0 bit configures USART as ReceiverĬonfiguring either of the bits(TXEN0 or RXEN0) overrides normal port functions of the corresponding pins ie GPIO pins are either configured as TXD or RXD.Enabling TXEN0 bit configures USART as Transmitter.USART Control and Status Register 0 B or UCSR0B contains the bits for configuring the USART as Transmitter,Receiver or Both. Since we are using the 8N1 format, we don't have to change anything as the default settings (0x06) gives 8N1 configuration. USART Control and Status Register 0 C or UCSR0C controls frame settings of the atmega328 USART. In our case we are using the 8N1 setup ie When a complete frame is transmitted, it can be directly followed by a new frame, or the communication line can be set to an idle (high) state. If enabled, the parity bit is inserted after the data bits, before the one or two stop bits. USART support the following combination of start/Stop/data/parity bits.įollowed by the data bits (from five up to nine data bits in total): first the least significant data bit, then the next data bits ending with the most significant bit. In our case we are using a crystal frequency of 11.0592MHz,the table below shows the corresponding UBBRn values,Error rates for a f OSCvalue of 11.0592MHz.Ī serial frame is defined to be a stream of data bits with synchronization bits (start and stop bits),and optionally a parity bit for error checking. If you check the table in the datasheet,you can find that error rates are close to zero when you are using fractional clock rates (f OSC) like 1.84MHz,3.68MHz,7.37MHz or 11.0592MHz. UBBRn values under U2Xn =1 column are for double the USART transmission speed which you can ignore. The ATmega328p datasheet has a section on commonly used Baud rates,Error rates,Crystal Frequencies and their corresponding UBBRn values.You can look up that table on the datasheet and select your desired UBBRn values. The required baudrate can be selected by writing the corresponding value to the UBBRn register. USART supports all commonly used baud rates from 2400 bps to 230.4kps without any issues.You can go up to 2.5Mbps for a crystal frequency of 20MHz.The maximum we are able to achieve on a Windows7 machine is 230.4k bps. Enabling the Transmitter or Receiver depending upon the usage.The USART has to be initialized before any communication can take place.The initialization process consists of the following steps. In our case we will be dealing only with asynchronous communication. Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) is a configurable peripheral of ATmega328p which supports both Synchronous (SPI) and asynchronous(Serial) communication protocols. Since the PC cannot receive the UART signals directly from the ATmega328P microcontroller,a USB to Serial Converter based on FT232RL is used to convert the serial TTL signals to USB Protocol. The following block diagram shows the hardware connections of the setup. RXD of ATmega328 is connected to TXD of USB to Serial Converter.TXD of ATmega328 is connected to RXD of USB to Serial Converter.You can check this tutorial to learn how to configure ATmega328 to use an external crystal as clock source. If you are using the 28 pin DIP version,please make sure that the pin numbers match by referring to the data sheet of ATmega328p.ĪTmega328p is clocked with an external Quartz crystal running at 11.0592MHz. We are using a 32 pin TQFP version of the ATmega328p microcontroller. All Source codes including "Make" files are available on our Github Repo.Hex code is uploaded into Atmega328p with AVRDUDE using USBasp Programmer.The code for the microcontroller section is written in embedded C and compiled using AVR-GCC (WinAVR).If you are looking for ATmega RS485 Communication check this tutorial. The data will be received/transmitted by a terminal emulation program like PuTTY or Tera Term. The ATmega328p microcontroller will send and receive data (ASCII Strings) to a PC running either a Linux or Windows operating system using it's (ATmega328p) UART pins. In this tutorial we will learn how to program the USART(uart) of ATmega328P microcontroller to communicate with a Linux/ Windows PC using asynchronous serial communication protocol. ![]()
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