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hello.ftdi.16E5.echo.c
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Neil Gershenfeld authoredNeil Gershenfeld authored
hello.ftdi.16E5.echo.c 5.24 KiB
//
// hello.ftdi.16E5.echo.c
//
// 16E5 115200 baud FTDI character echo, with flash string
//
// Neil Gershenfeld
// 10/27/15
//
// (c) Massachusetts Institute of Technology 2015
// 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 VPORTA VPORT0 // pre-mapped virtual port A
#define VPORTC VPORT1 // pre-mapped virtual port C
#define VPORTD VPORT2 // pre-mapped virtual port D
#define VPORTR VPORT3 // pre-mapped virtual port R
#define serial_port VPORT2.OUT
#define serial_direction VPORT2.DIR
#define serial_pins VPORT2.IN
#define serial_pin_in PIN6_bm
#define serial_pin_out PIN7_bm
#define led_port VPORT0.OUT
#define led_direction VPORT0.DIR
#define led_pin PIN4_bm
#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 up clock
//
OSC.CTRL = OSC_RC32MEN_bm; // enable 32MHz clock
while (!(OSC.STATUS & OSC_RC32MRDY_bm)); // wait for clock to be ready
CCP = CCP_IOREG_gc; // enable protected register change
CLK.CTRL = CLK_SCLKSEL_RC32M_gc; // switch to 32MHz clock
//
// initialize output pins
//
set(serial_port, serial_pin_out);
output(serial_direction, serial_pin_out);
output(led_direction, led_pin);
//
// main loop
//
index = 0;
while (1) {
get_char(&serial_pins, serial_pin_in, &chr);
set(led_port, led_pin);
put_string(&serial_port, serial_pin_out, "hello.ftdi.16E5.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
clear(led_port, led_pin);
}
}