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Tips and questions relating to the GPS modules from SFE
By carlton1212
So i purchased the ADH8066 module and breakout board and this is turning out to be tougher then i expected. I dont want to give it more voltage or amperage then it requires because im afraid i will fry it but one guy is saying no matter how much amperage i connect to it it will not fry cause it only draws what it needs. Here is the datasheet ... onv1.3.pdf

But do i have to make the manufacture power supply reference circuit on page 9 to power it. I was thinking of just using an adjustable electronic regulator to output 4v electricity then taking down the amperage after its leaves the regulator then putting in two 330 uF capacitors in parallel off the regulator output to meet the 2A transmission spike. I think this would work.

But even after i get it powered how do i get it compatible with the 5v GPIO pins of an avr microcontroller. I heard it was compatible with arduino in the comments section and bought it because i thought it was TTL compatible. Now its seeming like i wasted 70$.

On page 17 it shows the MCU GPIO pins as outputting 4v....which is not the case for any microcontroller. They all output 5v. So i have to buy a 3$ voltage regulator for each pin that i connect to the gsm breakout board???? But will regulating the voltage down cause me to lose the data contained in the output from the mcu? I'm thinking this would distort any bytes that i send to the gsm module. Thats insane and bulky.

Or would the regulated voltage still have binary logic in the since that 0 represents a mark or space and 4V represents a mark or space. I'm still kinda imagining the regulator as distorting any binary output from the MCU. How can i communicate an mcu with this gsm module?

In addition to all of the above just to power on/off the device i have to accomplish the requirements on page 18 to power the device on or off...which will require me to regulate the voltage down to 4v so the gsm module will accept it. Can you all help me with this and tell me what i am assuming correctly and what else i need to do or what i could do better.

By ezflyr

The basic nature of your questions suggests that this might be an overly ambitious project for you? If you decide to proceed, I'd take a look at the Sparkfun ADH8066 Evaluation Board:

The easiest was to deal with the voltage level requirements of the ADH8066 is to power the module and your MCU from the same 3.8V supply. This eliminates the need for voltage level conversion between the two. If run your MCU at 5V, you'll need to level shift the TxD and Rxd connections. From the MCU to the ADH8066 you can use a resistive voltage divider to reduce the voltage, but from the ADH8066 to the MCU, you'll need something like a transistor buffer. It's doable, but save yourself the headache and run the MCU at 3.8V.

You can apply an overvoltage to a circuit, but you can't apply an "overcurrent" - the circuit will only draw the current it's designed to draw. Think about the headlights on your car. They are connected to the same battery that can supply 100's of amps to the starter, but they only draw a few amps themselves!