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Transmitter/Receiver

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Spasm

New Member
Hi.
Can anyone tell me where to find info on coupling transmitter/receiver to microcontrollers?


Thanx

ps. SOrry...posted this twice
 

Pilot

New Member
Can anyone tell me where to find info on coupling transmitter/receiver to microcontrollers?
Please be more specific. The more information you give increases your chances of receiving suitable answers.

What have you got so far? What Tx/Rx?

What do you want to do? What kind of control?

Have you looked at microcontroller manufacturers websites to try and find datasheets and applications notes?
 

Spasm

New Member
Hi.
I'm actually interested in building a system whereby using microcontroller to control transmission to another microcontroller using RF signal. But the problem is I'm not sure how to couple the microcontroller to a transmitter and vice versa.Do I use a DAC/ADC to change the signal from microcontroller to the transmitter? Or is there any other alternative?

Thanx
:D
 

Chippie

Member
Your aims seem to be too non specific.........


For the transmitter, the rf module will accept the output from a micro as long its a standard that the transmitter accepts........

The receiver will output the results to a micro which will then function in accordance with its instruction....

We need a little more info in order to be specific with the assistance you require 8)
 

Spasm

New Member
Hi all.

Lets say I want to send signal from the microcontroller wirelessly to another microcontroller. What I'm not too sure about is how do I change the digital output from the microC for transmission using standard radio transmitters/receivers. Can anyone tell me where I can read about this type of modulation and what is the hardware involved. I'm new to this area and therefore I'm not sure whether transmitters are able to receive the digital input and sends out the transmission.

Thank You
 

Chippie

Member
Ok, I can make sense of this now :lol:


For instance, you can code a micro, to emit a digital signal. This signal may be the result of an input into the micro from say a keypad..
The digital signal is sent to the transmitter where it is modulated onto a carrier, AM or FM whatever, the receiver then receives the signal,and passes it to another micro, whose coding could be say to switch a solenoid operated lock, upon receipt of a valid code......


If you have a search for Radiometrix modules on the web, I'm sure you will find appication data....If you struggle, ask again, I may have something somewhere..... 8)
 

Spasm

New Member
Thank you masta Chippie for the info..Yeah..thats actually what i wanted to do..data transmission.
But Chippie..does the Tx/Rx u had mentioned has a DAC/ADC converter all build in? How bout for other Tx/Rx? Can I just put the output digital signal straight into the input for the Tx??

By the way do you know anyone that had already done a similar project like this?
I can't seem to find any...

Thanx
 

Chippie

Member
No dacs/adcs needed, just plug the data stream straight into the input of the tx, and extract from the rx.....

As for apps I'll have a dig thru my notes and see what I got.... 8)
 

pebe

Member
Spasm said:
Thank you masta Chippie for the info..Yeah..thats actually what i wanted to do..data transmission.
But Chippie..does the Tx/Rx u had mentioned has a DAC/ADC converter all build in? How bout for other Tx/Rx? Can I just put the output digital signal straight into the input for the Tx??

By the way do you know anyone that had already done a similar project like this?
I can't seem to find any...

Thanx
Hi Spasm,

This is not a difficult operation, but as a radio link can only carry one bit at any time, you will have to send the data serially. The idea is that the 8 bits that make up the contents of a register are shifted out, one bit at a time, onto one of the port o/p pins of the micro (uC1) and sent to the transmitter.

If you have more than 1 register to send then you need some way of identifying the beginning and end of each byte. The accepted way of doing that is to have the o/p pin normally sitting low ie. a 0. When you send the byte you add a start bit before the data. This means you take the pin high (1) for one bit period, then send the 8 bits and follow them by at least one bit period at 0 as a stop bit. That is the standard protocol when communicating with a computer, but for uC to uC, you dont have to stick with that, ie. You can send words 16 bits long if you like.

At the micro that is being used to receive the signal (uC2), the radio receiver would feed into an input pin that is constantly watched for incoming data. If the sole purpose of uC2 was to look for data and act on it, then OK. But the chances are it will be doing other things as well. The answer then would be to arrange in the software for the input pin to cause an interrupt whenever data arrived. The uC could then interrupt whatever task it was doing at the time to service the interrupt and read in the data. You can write subroutines to read or write out the data serially.

You can see that the data would be a stream of noughts and ones. The radio tx and rx would depend on how far you want to transmit, cost, and reliability.

For short distances you can pick a simple AM transmitter. There is one type that is just a blob with 2 connections. You put volts on to it and it transmits; take the volts off and it stops! You cannot get mush simpler than that for a simple on/off digital signal. The receiver is a simple AM one.

For longer distances where interference may be a problem you would be advised to go for FM, but the costs are a bit more. No doubt there are others who could advise you better.

I hope thats not too longwinded
 

Spasm

New Member
Hi pebe.
Thanx for the info on transmitting the data. I'm still gathering more information about which type of Tx/Rx to use.
Btw.. For transferring data between micro..lets say text msgs..is the 68hc11 with 512 bytes memory enough for this operation? I've tried searching at motorola sites but cant seem to decide on which microP to use..any suggestions?

Thanx
 

Chippie

Member
If you got access to a pic programmer I may be able to sort out some pic code for a 16F84.......how does that suit you ?
 

pebe

Member
Spasm said:
Hi pebe.
Thanx for the info on transmitting the data. I'm still gathering more information about which type of Tx/Rx to use.
Btw.. For transferring data between micro..lets say text msgs..is the 68hc11 with 512 bytes memory enough for this operation? I've tried searching at motorola sites but cant seem to decide on which microP to use..any suggestions?

Thanx
I'm not familiar with the 68hc11 series (I major on the ST62 series) so Ive just looked up the data sheet. I see the 69hc11e** chips have 512K of RAM. Remember that 1 character in your text message will use 1 byte. Depending on your program you may need up to 30 registers for timer data, flags etc., so think of probably 480 characters for your messages. The max characters will depend on whether you intend to hold the entire message in memory before transmitting it.
 

Spasm

New Member
Chippie.. i didnt learn about pic programming..i know how to program basic assembly for 68hc11 only :(

pebe..ohh...okay...thanx for the info..btw..how many times do u think the program should retransmit before the receiver side gets the data?


Thanx
 

mkd

New Member
Spasm said:
Chippie.. i didnt learn about pic programming..i know how to program basic assembly for 68hc11 only :(

pebe..ohh...okay...thanx for the info..btw..how many times do u think the program should retransmit before the receiver side gets the data?


Thanx
hello, I don't speak English, so, excuse me if I make many grammar mistakes, I am using a translator program.

I am thinking about using a mc68hc11e1cp2 with external memory and a pair of radiometrix modules, in half duplex way.

The radiometrix module can be directly connected to a port D pin, RX and TX of SCI subsystem, using a normal serial comunication mode.

Data error detection and correction has to be done inside of the microcontroller, and I am elaborating a communication protocol for my modules.

I intend to use packages of data of 8 bytes, where a byte will contain confirmation information and error correction.

The connection through radio uses the common serial protocol and I use two aditional pin, onte to select the way of operation of the module, if it is transmission or reception, and one to monitor the Radiometrix module.
 
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