6. Advanced Features

1. Sleep Timer.

EEPROM SETTINGS USED: 35, 36, 40

When the Geogram ONE is running at full power it draws a significant amount of current which limits the time the device can operate on a single charge of the main battery. The Geogram ONE has the ability to power down/sleep specific subsystems on the main board which, in turn, can reduce the power consumption of the device and further extend the battery life.
The three main onboard subsystems are:

• GPS Engine which is responsible for download coordinate information from the satellites in orbit.
• GSM (cellular IC) which is responsible for all communications over the cellular network.
• Microcontroller which is the onboard processor

There are two EEPROM settings that control the timer with regards to sleep functions: Sleep Time On and Sleep Time Off. Sleep Time On, in seconds, defines how long the device will stay awake functioning normally. Sleep Time Off, in seconds, defines how long the device will power down in sleep mode. Example, setting sleep time on to 3600 and sleep time off to 3600 will force the device to sleep for one hour and be awake for the next hour. This sequence would then continue to repeat itself. If running purely off the battery, these setting in essence would double the battery life. Setting either one of these parameters to a zero will disable the sleep function completely.

The next setting that affects the sleep timer is the Sleep Configuration setting. This EEPROM setting determines which of the subsystems will be put to sleep when the device enters sleep mode. The two primary subsystems that can be configured to sleep are the GPS and GSM. The microcontroller subsystem will always enter sleep mode regardless of the configuration settings. It also controls the sleep function overrides which will be discussed further below.

In addition to being able to put different subsystems to sleep, the Geogram ONE also has the ability to override these sleep functions using two different overrides.

The first override is motion. Since the GO has an onboard accelerometer (can detect small movements), it can be programmed to wake the device up if any motion is detected. This can be useful if a power source is not readily available to recharge the main battery.

The second override is the charging source. As mentioned above, the GO uses a significant amount of power during normal operation. When the device is solely running off the battery it is important to minimize power draw. When the device is connected to a power source capable of recharging the main battery, power consumption is not as important. The reason being is the recharge source can charge the battery faster than the maximum current draw.

Below are some sample application settings and their associated impacts on battery performance. Performance specs are based off average idle current draw of 35mA with all subsystems powered on using a standard 1500mAh battery that is not connected to a charging circuit. Putting all subsystems into sleep mode will also reduce battery consumption to 0.45mA. Based off these values the Geogram ONE has the ability to run for roughly 43 hours while fully awake and over 3000 hours while fully asleep. Please keep in mind these are just estimates.

	Example 1:

Sleep Time On = 3600 seconds (60 minutes)

Sleep Time Off = 0 seconds (0 minutes)

Power draw (mAh) = (60/60 * 35) + (0/60 * 0.45) = (35 mA) + (0 mA) = 35

Total Battery Life = (1500 / 35) = 42.86 hours

	Example 2:

Sleep Time On = 1800 seconds (30 minutes)

Sleep Time Off = 1800 seconds (30 minutes)

Power draw (mAh) = (30/60 * 35) + (30/60 * 0.45) = (17.5 mA) + (0.225 mA) = 17.725

Total Battery Life = (1500 / 17.725) = 84.6 hours

	Example 3:

Sleep Time On = 300 seconds (5 minutes)

Sleep Time Off = 3300 seconds (55 minutes)

Power draw (mAh) = (5/60 * 35) + (55/60 * 0.45) = (2.92mAh) + (0.4125mAh) = 3.3245

Total Battery Life = (1500 / 3.3245) = 451 hours

	Example 4:

Sleep Time On = 300 seconds (1 minutes)

Sleep Time Off = 3300 seconds (59 minutes)

Power draw (mAh) = (1/60 * 35) + (59/60 * 0.45) = (0.583mAh) + (0.4425mAh) = 1.0258

Total Battery Life = (1500 / 1.0258) = 1462 hours

2. Digital/Analog IO pins

EEPROM SETTINGS USED: 5, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 249, 265

The Geogram ONE has several digital/analog IO pins that give the user the ability to access the outside world. There are two dedicated digital pins (D4 and D10), three pins that can be configured as analog in or digital IO pins (A1 – A3). There is also a single pin that is dedicated as analog input only (A6).

When a pin is configured as a digital output it can switch between two different states, LOW (0 volts) and HIGH (3.3 volts). When a pin is configured as a digital input it is capable of reading a signal that is LOW (0 volts) or HIGH (3.3 volts). When a pin is configured as an analog input it is capable of reading a voltage range from 0 to 3.3 volts and returning a value from 0 to 1023.

Digital pins D4 and D10 can also be configured as interrupt driven inputs. The digital pin will be pulled to a HIGH level via an internal pullup resistor and when connected to ground (LOW) the message stored in EEPROM will be sent to the default SMS number that is stored in EEPROM.