Making your own microcontroller

[soninja8]

Hi, I was wondering if anyone can inform me on how to put a 75mhz crystal on the homemade augmented microcontroller, so i can use it just like a receiver...

[Soeren]

Hi,

Hi, I was wondering if anyone can inform me on how to put a 75mhz crystal on the homemade augmented microcontroller, so i can use it just like a receiver...

You don't make your own microcontroller, you by a ready made one, but you probably mean that you wanna make a microcontroller board.

75mHz is pretty slow (doesn't exist actually), so you probably mean 75MHz (Yes case matters).

For a couple of reasons, you cannot just add a 75MHz x-tal and make a controller a receiver.
First, you need a controller that is able to run at a suitable speed. While they exist, it's not something you want to start out with.
Then the signal from the antenna is in the µV range, so won't have a chance of making a controller do anything at all.

A 75MHz signal would, as the bare minimum need a speed of slightly over 150 MIPS and if you want to decode the signal, you'd need at least 750 MIPS, which leaves you with only 5 samples in each half period of a 50% duty cycle signal, so would have +/-20% accuracy.


If you just make or buy a plain old analog receiver and demodulator, you can feed the resulting signal into whatever controller you use and just handle the demodulated signal - no reason to try pulling the carrier into the controller.

[soninja8]

Ok, I dont much understand the big words, but I want to say that I have a 75mhz receiver and 75mhz crystal (channel 67 i believe), I never knew that you can use that with a microcontroller... http://www.robotshop.com/dfrobot-romeo-all-in-one-microcontroller-atmega-328-4.html is the microcontroller I want, Is there a way to use my 75mhz receiver and crystal with the microcontroller, so I can control it with my transmitter, AND have sensors and the such? Im a beginner so it would be awesome if you can use small words
Thanks,
Soninja8

[MikeK]

I think 75MHz is a popular frequency for radio controlled cars or planes?  You might be able to get a cheap toy, perhaps one with a broken wing or such, and use the receiver in conjunction with the microcontroller.  The microcontroller is just going to deal with the signal (message) instead of the carrier.

[soninja8]

I already have a receiver and a transmitter, i was wondering if there was any way to add that to a microcontroller

This is the exact one I have 75mhz receiver and crystal ----->

[Soeren]

Hi,

Ok, I dont much understand the big words, but I want to say that I have a 75mhz receiver and 75mhz crystal (channel 67 i believe),

What receiver is it?
How many channels?
Have you got a link to it?

Is there a way to use my 75mhz receiver and crystal with the microcontroller, so I can control it with my transmitter, AND have sensors and the such? Im a beginner so it would be awesome if you can use small words

Yes, you can feed each of the receivers servo outputs to an input pin and your program then needs to check and decode these inputs.
Google "servo signal" and read all you can about how a servo is controlled.

It will be a while before you are able to do this however, so concentrate on getting the controller to do your bidding first.

[soninja8]

Yes, you can feed each of the receivers servo outputs to an input pin and your program then needs to check and decode these inputs.

Umm...feed the servo imputs to the receiver and the microcontroller? or to one or the other? do i need a Y cable to split it?

[rbtying]

Receiver outputs connect to microcontroller inputs.  In turn, the microcontroller connects to motors/sensors/servos/etc.

[soninja8]

Which inputs do i plug the receiver into? how would there be enough room for the servos and the receiver to plug in?

[Soeren]

Hi,

Which inputs do i plug the receiver into? how would there be enough room for the servos and the receiver to plug in?

Since you didn't answer my question on what you have, for this example I am assuming a 4 channel receiver, for which you'll need 8 pins.

The receiver has got a 3 pin connectors for each servo. one pin is the signal, one is Gnd and the last one is V+
You just need to connect a single Gnd to the Gnd of the controller and the V+ shouldn't be connected, which leaves the 4 signal pins that goes to inputs on the controller.

The servos needs 1 signal each, so that's 4 outputs (the V+ and Gnd doesn't take pins from the controller).