Issue in Serial Communication

Objective: Program ATTiny44 to send AT Commands to ESP8266-12E SMD.

• I'm using parts of Neil's hello.ftdi.44.echo.c
• Programming environment Arduino IDE using Arduino as ISP
• Board Configuration (External 20MHz) : https://github.com/SpenceKonde/ATTinyCore

Issue: Inconsistent and Incorrect parsing of serial data.

Code

#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 serial_port PORTA
#define serial_direction DDRA
#define serial_pins PINA
#define serial_pin_in (1 << PA1)
#define serial_pin_out (1 << PA0)

#define max_buffer 25

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);
   }

void setup() {
  DDRB |= (1 << PB2); 
  // put your setup code here, to run once:
   static char chr;
   static char buffer[max_buffer] = {0};
   static int index = 0;
   //
   // 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);
   put_string(&serial_port, serial_pin_out, "AT+CWMODE=1\r\n" );
   delay(500);
   put_string(&serial_port, serial_pin_out, "AT+CWJAP=\"SeeknFind\",\"nill1123\"\r\n" );
   delay(500);
}

void loop() {
  PORTB |= (1 << PB2);
  // put your main code here, to run repeatedly:
  delay(1000);
  put_string(&serial_port, serial_pin_out, "AT+CIPMUX=1\r\n" );
  PORTB = 0;
  delay(2000);
}

Output

(Loading image....)