{"id":2311,"date":"2024-07-16T15:47:37","date_gmt":"2024-07-16T15:47:37","guid":{"rendered":"https:\/\/iotthinghub.com\/?p=2311"},"modified":"2024-08-12T12:44:12","modified_gmt":"2024-08-12T12:44:12","slug":"uart","status":"publish","type":"post","link":"https:\/\/iotthinghub.com\/?p=2311","title":{"rendered":"UART"},"content":{"rendered":"\n

USART stands for Universal Synchronous Asynchronous Transmitter and Receiver in which a packet of data enclosed in an envelope of start and stop bit. Synchronous means that single clock source would be shared by end devices to facilitate communication and asynchronous means, there would be no synchronous clock source would be the end of the device. To allow the communication between two devices we need to decide a bound rate. Here bound rate is the speed of your communication and is measured in bits per second. Let\u2019s look at the USART register available in AVR and there uses-<\/p>\n\n\n\n

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Initialize USART<\/p>\n\n\n\n

Initialize USART is very simple. Just initialize the following condition<\/p>\n\n\n\n

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Thus for BAUD RATE=9600 with F_CPU=8MHz, the UBRR value is 51. If U2X bit is enabled then simply multiply 2 with UBRR value.<\/p>\n\n\n\n

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  1. Enable Transmit or Receive mode with either Synchronous or Asynchronous operation <\/li>\n\n\n\n
  2. Select the character frame size with parity and stop bit.<\/li>\n<\/ol>\n\n\n\n

    Let\u2019s enable USART mode with BAUD RATE=9600, F_CPU=8MHz, Asynchronous mode, 8 bit character with no parity and 1 stop bit. From the above calculation UBRR=51.<\/p>\n\n\n

    \nvoid usart_init(void)\n{\n  UBRR0=(uint8_t)51; \/\/UBRR0H=0;\n  \/******  Asynchronous mode, 8 bit character with no parity and 1 stop bit *******\/\n  UCSRB|=(1<<RXEN)|(1<<TXEN);\n  UCSRC|=(1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0); \/\/For UCSRC register selection URSEL bit is set.\n}\n<\/pre><\/div>\n\n\n
    Send individual indications<\/p>\n\n\n\n
    Since the UDR register is full duplex, data can be transmitted by writing this register and data can be received by reading this register. To send data just write the data to UDR and it automatically send via AVR Tx pin. Now wait until the transmission complete either checking the TXC or UDRE bit in UCSRA register. Since the flag register is set when data send completed. So the checking condition is<\/p>\n\n\n\n
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    \nUDR=ByteToSend;\nwhile(!(UCSRA&(1<<TXC)))\n{\n;\/\/ wait until data send\n}\n\n<\/pre><\/div><\/div>\n\n\n\n
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    <\/p>\n\n\n\n
    OR<\/p>\n<\/div>\n\n\n\n
    \nUDR=ByteToSend;\nwhile(!(UCSRA&(1<<UDRE)))\n{\n;\/\/ wait for possible sending\n}\n\n<\/pre><\/div><\/div>\n<\/div>\n\n\n\n