// // hello.ftdi.45.echo.c // // tiny45 echo hello-world // 9600 baud FTDI interface // // Neil Gershenfeld 11/17/19 // // This work may be reproduced, modified, distributed, // performed, and displayed for any purpose, but must // acknowledge this project. Copyright is retained and // must be preserved. The work is provided as is; no // warranty is provided, and users accept all liability. // #include #include #define output(directions,pin) (directions |= pin) // set port direction for output #define input(directions,pin) (directions &= (~pin)) // set port direction for input #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 102 // bit delay for 9600 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 serial_port PORTB #define serial_direction DDRB #define serial_pins PINB #define serial_pin_in (1 << PB2) #define serial_pin_out (1 << PB1) #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 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.45.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 } }