Not a member of Pastebin yet?
Sign Up,
it unlocks many cool features!
- //
- //
- // hello.ftdi.44.echo.c
- //
- // 115200 baud FTDI character echo, with flash string
- //
- // set lfuse to 0x5E for 20 MHz xtal
- //
- // Neil Gershenfeld
- // 12/8/10
- //
- // (c) Massachusetts Institute of Technology 2010
- // This work may be reproduced, modified, distributed,
- // performed, and displayed for any purpose. Copyright is
- // retained and must be preserved. The work is provided
- // as is; no warranty is provided, and users accept all
- // liability.
- //
- #include <avr/io.h>
- #include <util/delay.h>
- #include <avr/pgmspace.h>
- #define output(directions,pin) (directions |= pin) // set port direction for output
- #define set(port,pin) (port |= pin) // set port pin
- #define clear(port,pin) (port &= (~pin)) // clear port pin
- #define pin_test(pins,pin) (pins & pin) // test for port pin
- #define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
- #define bit_delay_time 8.5 // bit delay for 115200 with overhead
- #define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
- #define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
- #define char_delay() _delay_ms(10) // char delay
- #define serial_port PORTA
- #define serial_direction DDRA
- #define serial_pins PINA
- #define serial_pin_in (1 << PA0)
- #define serial_pin_out (1 << PA1)
- #define max_buffer 25
- void get_char(volatile unsigned char *pins, unsigned char pin, char *rxbyte) {
- //
- // read character into rxbyte on pins pin
- // assumes line driver (inverts bits)
- //
- *rxbyte = 0;
- while (pin_test(*pins,pin))
- //
- // wait for start bit
- //
- ;
- //
- // delay to middle of first data bit
- //
- half_bit_delay();
- bit_delay();
- //
- // unrolled loop to read data bits
- //
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 0);
- else
- *rxbyte |= (0 << 0);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 1);
- else
- *rxbyte |= (0 << 1);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 2);
- else
- *rxbyte |= (0 << 2);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 3);
- else
- *rxbyte |= (0 << 3);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 4);
- else
- *rxbyte |= (0 << 4);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 5);
- else
- *rxbyte |= (0 << 5);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 6);
- else
- *rxbyte |= (0 << 6);
- bit_delay();
- if pin_test(*pins,pin)
- *rxbyte |= (1 << 7);
- else
- *rxbyte |= (0 << 7);
- //
- // wait for stop bit
- //
- bit_delay();
- half_bit_delay();
- }
- void put_char(volatile unsigned char *port, unsigned char pin, char txchar) {
- //
- // send character in txchar on port pin
- // assumes line driver (inverts bits)
- //
- // start bit
- //
- clear(*port,pin);
- bit_delay();
- //
- // unrolled loop to write data bits
- //
- if bit_test(txchar,0)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,1)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,2)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,3)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,4)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,5)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,6)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- if bit_test(txchar,7)
- set(*port,pin);
- else
- clear(*port,pin);
- bit_delay();
- //
- // stop bit
- //
- set(*port,pin);
- bit_delay();
- //
- // char delay
- //
- bit_delay();
- }
- void put_string(volatile unsigned char *port, unsigned char pin, char *str) {
- //
- // print a null-terminated string
- //
- static int index;
- index = 0;
- do {
- put_char(port, pin, str[index]);
- ++index;
- } while (str[index] != 0);
- }
- int main(void) {
- //
- // main
- //
- static char chr;
- static char buffer[max_buffer] = {0};
- static int index;
- //
- // set clock divider to /1
- //
- CLKPR = (1 << CLKPCE);
- CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
- //
- // initialize output pins
- //
- set(serial_port, serial_pin_out);
- output(serial_direction, serial_pin_out);
- //
- // main loop
- //
- index = 0;
- while (1) {
- get_char(&serial_pins, serial_pin_in, &chr);
- put_string(&serial_port, serial_pin_out, "hello.ftdi.44.echo.c: you typed \"");
- buffer[index++] = chr;
- if (index == (max_buffer-1))
- index = 0;
- put_string(&serial_port, serial_pin_out, buffer);
- put_char(&serial_port, serial_pin_out, '\"');
- put_char(&serial_port, serial_pin_out, 10); // new line
- }
- }
Add Comment
Please, Sign In to add comment