stk500_recv(): programmer is not responding

this is the program uploaded
after uploading, the current was measured at ~24ma using a meter and 4- AA batteries which was a circuit used often
to read current without prior problems or error messages.
Then, the blink program was uploaded and the error message appeared: avrdude:stk500_recv(): programmer is not responding

PROGRAM:

#include <avr/sleep.h>

/* Sleep Demo Serial


  • Example code to demonstrate the sleep functions in an Arduino.
  • use a resistor between RX and pin2. By default RX is pulled up to 5V
  • therefore, we can use a sequence of Serial data forcing RX to 0, what
  • will make pin2 go LOW activating INT0 external interrupt, bringing
  • the MCU back to life
  • there is also a time counter that will put the MCU to sleep after 10 secs
  • NOTE: when coming back from POWER-DOWN mode, it takes a bit
  • until the system is functional at 100%!! (typically <1sec)
  • Copyright (C) 2006 MacSimski 2006-12-30
  • Copyright (C) 2007 D. Cuartielles 2007-07-08 - Mexico DF
  • This program is free software: you can redistribute it and/or modify
  • it under the terms of the GNU General Public License as published by
  • the Free Software Foundation, either version 3 of the License, or
  • (at your option) any later version.
  • This program is distributed in the hope that it will be useful,
  • but WITHOUT ANY WARRANTY; without even the implied warranty of
  • MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  • GNU General Public License for more details.
  • You should have received a copy of the GNU General Public License
  • along with this program. If not, see http://www.gnu.org/licenses/.

*/

int wakePin = 2; // pin used for waking up
int sleepStatus = 0; // variable to store a request for sleep
int count = 0; // counter

void wakeUpNow() // here the interrupt is handled after wakeup
{
// execute code here after wake-up before returning to the loop() function
// timers and code using timers (serial.print and more…) will not work here.
// we don’t really need to execute any special functions here, since we
// just want the thing to wake up
}

void setup()
{
pinMode(wakePin, INPUT);

Serial.begin(9600);

/* Now it is time to enable an interrupt. In the function call

  • attachInterrupt(A, B, C)
  • A can be either 0 or 1 for interrupts on pin 2 or 3.
  • B Name of a function you want to execute while in interrupt A.
  • C Trigger mode of the interrupt pin. can be:
  • LOW a low level trigger
  • CHANGE a change in level trigger
  • RISING a rising edge of a level trigger
  • FALLING a falling edge of a level trigger
  • In all but the IDLE sleep modes only LOW can be used.
    */

attachInterrupt(0, wakeUpNow, LOW); // use interrupt 0 (pin 2) and run function
// wakeUpNow when pin 2 gets LOW
}

void sleepNow() // here we put the arduino to sleep
{
/* Now is the time to set the sleep mode. In the Atmega8 datasheet

  • http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf on page 35
  • there is a list of sleep modes which explains which clocks and
  • wake up sources are available in which sleep mode.
  • In the avr/sleep.h file, the call names of these sleep modes are to be found:
  • The 5 different modes are:
  • SLEEP_MODE_IDLE -the least power savings
  • SLEEP_MODE_ADC
  • SLEEP_MODE_PWR_SAVE
  • SLEEP_MODE_STANDBY
  • SLEEP_MODE_PWR_DOWN -the most power savings
  • For now, we want as much power savings as possible, so we
  • choose the according
  • sleep mode: SLEEP_MODE_PWR_DOWN

*/
set_sleep_mode(SLEEP_MODE_PWR_DOWN); // sleep mode is set here

sleep_enable(); // enables the sleep bit in the mcucr register
// so sleep is possible. just a safety pin

/* Now it is time to enable an interrupt. We do it here so an

  • accidentally pushed interrupt button doesn’t interrupt
  • our running program. if you want to be able to run
  • interrupt code besides the sleep function, place it in
  • setup() for example.
  • In the function call attachInterrupt(A, B, C)
  • A can be either 0 or 1 for interrupts on pin 2 or 3.
  • B Name of a function you want to execute at interrupt for A.
  • C Trigger mode of the interrupt pin. can be:
  • LOW a low level triggers
  • CHANGE a change in level triggers
  • RISING a rising edge of a level triggers
  • FALLING a falling edge of a level triggers
  • In all but the IDLE sleep modes only LOW can be used.
    */

attachInterrupt(0,wakeUpNow, LOW); // use interrupt 0 (pin 2) and run function
// wakeUpNow when pin 2 gets LOW

sleep_mode(); // here the device is actually put to sleep!!
// THE PROGRAM CONTINUES FROM HERE AFTER WAKING UP

sleep_disable(); // first thing after waking from sleep:
// disable sleep…
detachInterrupt(0); // disables interrupt 0 on pin 2 so the
// wakeUpNow code will not be executed
// during normal running time.

}

void loop()
{
// display information about the counter
Serial.print("Awake for ");
Serial.print(count);
Serial.println(“sec”);
count++;
delay(1000); // waits for a second

// compute the serial input
if (Serial.available()) {
int val = Serial.read();
if (val == ‘S’) {
Serial.println(“Serial: Entering Sleep mode”);
delay(100); // this delay is needed, the sleep
//function will provoke a Serial error otherwise!!
count = 0;
sleepNow(); // sleep function called here
}
if (val == ‘A’) {
Serial.println(“Hola Caracola”); // classic dummy message
}
}

// check if it should go to sleep because of time
if (count >= 10) {
Serial.println(“Timer: Entering Sleep mode”);
delay(100); // this delay is needed, the sleep
//function will provoke a Serial error otherwise!!
count = 0;
sleepNow(); // sleep function called here
}
}

      delay(100);     // this delay is needed, the sleep
                      //function will provoke a Serial error otherwise!!

This band-aid is needed only if you don't flush the outgoing buffer, and wait for the last character to shift out.