Device Overview

The name, description and true functions of this device are currently classified by Splitmoon Productions until a patent has been issued. Sorry :(

Feature list

As mentioned previously, no details can be issued on the function of this project. However, since the components in use are relatively generic (and the design itself may perform many functions), an overview of the devices capablities are listed below.

You may have noticed the device is powered using a standard "Nokia knock-off" 3.7volt LiIon battery - yet a 4x20 HD44780 LCD module is present and requires 5 volts, so what's going on? The obvious solution was to use a boost-converter (sort of like a step-up transformer) - There are other less elegant solutions available for this problem, but why the need to complicate things further?

All in all, the device was tricky to put together. The microcontrollers require 3v3, the LCD module requires 5v, as does the flashdisk. Since the device MAY be powered from a vehicle, the only efficient solution was to use switchmode regulators to cut the voltages down to usable levels. The LT1308 regulator provides 5v from the 11-15v DC input, enough to power the battery charger, USB and LCD modules. A pair of TC1017 linear regulators chop the 5v down to 3v3 for use by the microcontrollers, EEPROM and support logic.

When powered from the battery input, the battery voltage is fed through an LT1308A boost converter (I love you Linear Technology!), which boosts the input voltage to 5 volts powering the system load and 3v3 regulators.

That's power handled, but what about the 3v3 logic of the microcontroller interfacing to the 5v logic of the LCD module?

Fortunately, the microcontroller is 5volt-input-tolerant on all it's Digital IO pins. UNFORTUNATELY, this only means I can "read" data from the LCD module at 5 volts. Writing to the LCD inputs (according to the LCD datasheet) requires at least 2/3 VCC for a logic HIGH to be reliably received. The solution was of course, to use level translator ICs. As I need to both read and write to the LCD module, ADG3304 Four channel BiDirectional level translators were used. ADG3308BRU (8 channel version) would have been better than using four '3304s, but I didn't have any on hand.

That pretty much covers all inidvidual segments of the design itself (bar the Realtime Clock and EEPROM, but they're self explanatory) - Unfurtunately getting into even more intricate detail would likely get me shot and possibly sued, not necessarily in that order. More info will be posted as it becomes available!