go_away

Author Topic: Type of data transfer between Tx/Rx 433Mhz wireless Modules  (Read 1686 times)

0 Members and 1 Guest are viewing this topic.

Offline pepco-boyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Type of data transfer between Tx/Rx 433Mhz wireless Modules
« on: October 01, 2012, 04:08:45 AM »
hi,

i have this project for measuring temperature using NTC termistor.

I'm using atmega32 and  Tx/Rx 433Mhz wireless Modules. on the Tx side i measure the temperature which is received on the Rx side where it is being displayed on LCD.

I'm using the ADC 10-bit mode of the atmega32 to measure the temperature but i can't get correct result on the LCD Rx side.

I tested it further and when i'm not using a wireless connection (measuring the temperature with 10-bit ADC and displaying it on LCD ) it works great! so i guess my calculations are ok and that's not it...

i'm not sure where exactly lies the problem, does somebody knows if it's possible to send a 10-bit data with such wireless modules? 

Offline Gertlex

  • Supreme Robot
  • *****
  • Posts: 744
  • Helpful? 23
  • Nuclear Engineer · Roboticist
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #1 on: October 01, 2012, 08:37:38 AM »
A link to the wireless modules you're using is absolutely necessary for anyone to help you... :)
I


Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #3 on: October 01, 2012, 01:14:20 PM »
Hi,

I'm using atmega32 and  Tx/Rx 433Mhz wireless Modules. on the Tx side i measure the temperature which is received on the Rx side where it is being displayed on LCD.

I'm using the ADC 10-bit mode of the atmega32 to measure the temperature but i can't get correct result on the LCD Rx side.
Sounds like you're trying to send the data as analog, but your transmitter is meant for digital data only.
Even if it could send an analog value, you wouldn't get any usable precision.

You have to process the data before transmitting it and then transmit the data digitally.

If 8 bit of A/D will do, a PIC10F2222 would be perfect for it and then you can linearize the NTC data before transmitting them with a minimal footprint.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

  • Supreme Robot
  • *****
  • Posts: 1,941
  • Helpful? 98
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #4 on: October 01, 2012, 03:42:56 PM »
They are a very simply ASK (OOK) transmitter/receiver. Even sending digital data, like you would on a serial COM port does not work.
Google ASK and OOK (Wiki has a good article) on how they work then look for example code the sends a 'pre-ample' and Manchester encodes/decodes the data.

As for your current code, hard wire the two processor's data lines (Tx to RX & RX to TX) to test the sending and receiving of the proper temperature data. Then add the code for the RF link and send simple know data (constant value or incrementing value) to get the RF link working. Last is sending the temperature data over the RF link.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #5 on: October 01, 2012, 06:28:40 PM »
Hi,

They are a very simply ASK (OOK) transmitter/receiver. Even sending digital data, like you would on a serial COM port does not work.
I have to disagree... They can be used to make a wireless no-handshake-232 (within the bps range it can handle), although a protocol with packetized checksum'd data and retransmission of bad packets gives a more secure transmission, but hey, this is temperature data and the receiver could accept only a certain deviation between two sets before discarding the last data sent.

Many wireless doorbells/oven thermometers/weather stations etc. use similar ASK modules and transmit simple digital data with no checksum or anything and they rarely fail, as long as they're in range and there's nothing jamming them.
(Makes me think... My SO likes her meat a little more rare than I do, so perhaps I should make a jammer/"translator" to get an oven roast more to my liking ;D)

For more secure transmissions, FSK is much better.


As for your current code, hard wire the two processor's data lines [...]
I might be wrong, but I got the idea that only the receiver side contains a controller.
« Last Edit: October 01, 2012, 07:01:54 PM by Soeren »
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline pepco-boyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #6 on: October 06, 2012, 01:43:28 AM »
both side RX and TX has controllers and i did manage to send the the termistor temperature data in the end with those modules 8 bit ADC data and also 10 bit ADC data., i just had to come up with a better packet sending technique, transmitting a certain sequence with one controller which is verified in the receiving side. now it's working pretty good except the exceptional noise deviations, i was wondering if somebody could give a hint about the best method for noise reduction using this kind of wireless modules?? 

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #7 on: October 09, 2012, 06:39:03 PM »
Hi,

[...] i was wondering if somebody could give a hint about the best method for noise reduction using this kind of wireless modules??
The noise that you see between transmissions is a direct consequence of how those cheap modules are made - their gain is raised until a signal is received at proper strength (or until it hits the limit), so in the absense of a valid signal, random noise will get through.
The only way to cure this noise is by using better (= more expensive) modules, using either FSK- or PSK modulation and perhaps a noise gate.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline waltr

  • Supreme Robot
  • *****
  • Posts: 1,941
  • Helpful? 98
Re: Type of data transfer between Tx/Rx 433Mhz wireless Modules
« Reply #8 on: October 09, 2012, 07:23:14 PM »
Hi,

[...] i was wondering if somebody could give a hint about the best method for noise reduction using this kind of wireless modules??

The noise that you see between transmissions is a direct consequence of how those cheap modules are made - their gain is raised until a signal is received at proper strength (or until it hits the limit), so in the absense of a valid signal, random noise will get through.
The only way to cure this noise is by using better (= more expensive) modules, using either FSK- or PSK modulation and perhaps a noise gate.


Another method is to use a pre-ample that  runs the receiver's gain down and is then detected by the micro-control to start receiving.
http://www.atmel.com/images/doc9164.pdf
Here is good code for OOK TX/RX:
http://www.open.com.au/mikem/arduino/VirtualWire.pdf

 


Get Your Ad Here

data_list