Atmega Программный Uart
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I am using an Atmega32 to transmit data to a Raspberry Pi 2 via UART. The Atmega transmission code is in C and the RPi receiving code is in Python 2.7. Below is the Atmega C code. I use the function USARTTransmitString, which calls uartputc in the Atmega.
Routines for asynchronous UART communication on the ATMega328P
uart.c
| /* |
| * uart.c |
| * |
| * Asynchronous UART example tested on ATMega328P (16 MHz) |
| * |
| * Toolchain: avr-gcc (4.3.3) |
| * Editor: Eclipse Kepler (4) |
| * Usage: |
| * Perform all settings in uart.h and enable by calling initUART(void) |
| * Compile: |
| * make all |
| * |
| * Functions: |
| * - First call initUART() to set up Baud rate and frame format |
| * - initUART() calls macros TX_START() and RX_START() automatically |
| * - To enable interrupts on reception, call RX_INTEN() macros |
| * - Call functions getByte() and putByte(char) for character I/O |
| * - Call functions writeString(char*) and readString() for string I/O |
| * |
| * Created on: 21-Jan-2014 |
| * Author: Shrikant Giridhar |
| */ |
| #include'uart.h' |
| // Debug Mode; comment out on Release |
| #define_DEBUG0 |
| /*! brief Configures baud rate (refer datasheet) */ |
| voidinitUART(void) |
| { |
| // Not necessary; initialize anyway |
| DDRD = _BV(PD1); |
| DDRD &= ~_BV(PD0); |
| // Set baud rate; lower byte and top nibble |
| UBRR0H = ((_UBRR) & 0xF00); |
| UBRR0L = (uint8_t) ((_UBRR) & 0xFF); |
| TX_START(); |
| RX_START(); |
| // Set frame format = 8-N-1 |
| UCSR0C = (_DATA << UCSZ00); |
| } |
| /*! brief Returns a byte from the serial buffer |
| * Use this function if the RX interrupt is not enabled. |
| * Returns 0 on empty buffer |
| */ |
| uint8_tgetByte(void) |
| { |
| // Check to see if something was received |
| while (!(UCSR0A & _BV(RXC0))); |
| return (uint8_t) UDR0; |
| } |
| /*! brief Transmits a byte |
| * Use this function if the TX interrupt is not enabled. |
| * Blocks the serial port while TX completes |
| */ |
| voidputByte(unsignedchar data) |
| { |
| // Stay here until data buffer is empty |
| while (!(UCSR0A & _BV(UDRE0))); |
| UDR0 = (unsignedchar) data; |
| } |
| /*! brief Writes an ASCII string to the TX buffer */ |
| voidwriteString(char *str) |
| { |
| while (*str != '0') |
| { |
| putByte(*str); |
| ++str; |
| } |
| } |
| constchar* readString(void) |
| { |
| char rxstr[RX_BUFF]; |
| char* temp; |
| temp = rxstr; |
| while((*temp = getByte()) != 'n') |
| { |
| ++temp; |
| } |
| return rxstr; |
| } |
| #if _DEBUG |
| intmain(void) |
| { |
| initUART(); |
| while(1) |
| { |
| writeString(readString()); |
| putByte('r'); |
| putByte('n'); |
| } |
| return0; |
| } |
| #endif |
Atmega Chip
uart.h
| /* |
| * uart.h |
| * |
| * UART example for ATMega328P clocked at 16 MHz |
| * |
| * TODO :- |
| * - Implement string read function |
| * - Optimize for size |
| * - Add helper routines and compile to .a file |
| * |
| * Created on: 22-Jan-2014 |
| * Author: Shrikant Giridhar |
| */ |
| #ifndef UART_H_ |
| #defineUART_H_ |
| #include<avr/io.h> |
| #include<stdint.h> |
| /* Probably already defined somewhere else. Define here, if isn't. */ |
| #ifndef FOSC |
| #defineFOSC16000000UL |
| #endif |
| /* Settings */ |
| #define_BAUD9600// Baud rate (9600 is default) |
| #define_DATA0x03// Number of data bits in frame = byte tranmission |
| #define_UBRR (FOSC/16)/_BAUD - 1// Used for UBRRL and UBRRH |
| #defineRX_BUFF10 |
| /* Useful macros */ |
| #defineTX_START() UCSR0B = _BV(TXEN0) // Enable TX |
| #defineTX_STOP() UCSR0B &= ~_BV(TXEN0) // Disable TX |
| #defineRX_START() UCSR0B = _BV(RXEN0) // Enable RX |
| #defineRX_STOP() UCSR0B &= ~_BV(RXEN0) // Disable RX |
| #defineCOMM_START() TX_START(); RX_START() // Enable communications |
| /* Interrupt macros; Remember to set the GIE bit in SREG before using (see datasheet) */ |
| #defineRX_INTEN() UCSR0B = _BV(RXCIE0) // Enable interrupt on RX complete |
| #defineRX_INTDIS() UCSR0B &= ~_BV(RXCIE0) // Disable RX interrupt |
| #defineTX_INTEN() UCSR0B = _BV(TXCIE0) // Enable interrupt on TX complete |
| #defineTX_INTDIS() UCSR0B &= ~_BV(TXCIE0) // Disable TX interrupt |
| /* Prototypes */ |
| voidinitUART(void); |
| uint8_tgetByte(void); |
| voidputByte(unsignedchar data); |
| voidwriteString(char *str); |
| constchar* readString(void); |
| #endif/* UART_H_ */ |
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