Wireless modules and simple setup, what is required?

[tasmod]

Hi all,

I have a friend who has asked me to design a radio link for simple on/off control at 868MHz.

Now I've never even looked at this before so I'm unsure as to a simple solution.

I've seen data transceivers on ebay, but what would be best, I assume a simple data stream would be adequate.

If anyone has any idea of a suitable pair of +10dbm modules please post the details. I'm somewhat confused by the choice, with some as rs232 others mentioning uart etc.

The idea is to send to a remote location a signal to turn on/off an output. That's it, nothing fancy.

In software I guess a unique ID then a code to select the action. I also considered as I was considering a transcever pair, a signal back to confirm output selected.

Rob

[tasmod]

OK I've found Dave Houstons excellent examples page, now i guess I just need pointing at a suitable pair of modules.

+10dbm is needed for a longer reliable range, the antennas are no problem.

I'm still confused by the choice of module, i suppose I'm saying i'm too dumb to understand the different protocols :)

Incidentally, the choice of 868MHz was his, apparently the place where this is to be used is full of 433 devices and he wanted to avoid a clash.

[tasmod]

Found this transceiver module on Farnell.

Anyone tell me if it's suitable for this use. I see it has SPI, I2C and UART listed as protocols.

Zulu RF 868MHz Module (http://uk.farnell.com/rf-solutions/zulu-868/module-rf-trx-868mhz-2km/dp/2133433)

[tasmod]

Hmm noticed that one has abuilt in processor.

How about this one
high-power-radio-transceiver/ (http://shop.ciseco.co.uk/arf-high-power-radio-transceiver/)

3.3volt operation and logic levels ? Not sure on that one. Does a 16f628 at 3.3v working output at 3.3v logic levels. Sense says it should, although at bottom end of chips working voltage range.

Rob

[Chirpy]

if it's running at 3.3v, then yes, it'll output at 3.3 logic levels, and there's always the alternative of using something like a voltage divider with a 1.8k ohm and 3.3k ohm resistors if you need to convert the voltage from 5v to 3.3v.

[tasmod]

Thanks for that.

I've decided to go with the Ciseco hi power transceivers.

I've written some preliminary code based upon Dave Houstons code. I need to add prelim ID followed by string then acknowledgement just in case of power outage.

[Charlie]

OK I've found Dave Houstons excellent examples page, now i guess I just need pointing at a suitable pair of modules.
Can you post a link to the page you are talking about?

[mackrackit]

Mr. Houston's site
http://davehouston.net/

[mtripoli]

I just finished a project using Linx Technologies 900 MHz transceivers. Mouser has them: http://www.mouser.com/ProductDetail/Linx-Technologies/TRM-900-NT/?qs=sGAEpiMZZMuIes%252bYBRf57cVc9kc9jsxyrSQqdnUWL1 o%3d

Super simple to use - these are "air wires" meaning they don't force a fixed protocol on you; you can transmit/receive just about any kind of data you want (literally, serial, PWM, etc). This is a "big deal" if you don't want to get bogged down in the details of using a fixed protocol for your data.

As usual; the data sheet will be your best friend. They have demo systems available (I highly recommend buying the system to jumpstart your project - you can hook your uC to the board and be underway in minutes).

Good luck!

[Dick Ivers]

Hi mtripoli, What range distance are you aiming for with the Linx 900 mhz transceivers? Is your project one-way or two-way communication?

[mtripoli]

This application only required a range around 25 feet. We did an ad hoc test of the system and got more than a 300 foot range using a ~0.75" ceramic antenna internal to the "remote" unit and a stub ~3" antenna on the base unit connected to the PC. With larger antenna's I think the range would easily be 500 feet or more. These are transceivers and we are doing two way comms. Data transmission rates come into play when determining the max distance. As I said, this device is an "air wire"; you can send any kind of "pulsed data". You could send PWM to remotely control dimming, motor speed (don't know that I'd actually recommend that one though). The module itself is very powerful; you can use it under uC control or in a "dumb" mode. Check them out...

[flotulopex]

Hi Tasmod,

I'm finishing a similar project to yours with LINX RF modules (https://www.linxtechnologies.com/en/products/modules/lr-rf-transmitter-receiver).

I choose the 433MHz version to ensure better distance; I tested with a "Splatch" (from LINX too) antenna and reached easely 70 meters. I paid $13.- for the receiver (RXM-433-LR) and $8.- for the transmitter (TXM-433-LR) module.

These RF modules are super-simple to use and it took me less than an hour from unpacking them to have sent the first data :)

I made this short (simplified testing) code fot the Transmitter:

' Fuses PIC12F675 - 4MHz XTal
@ __CONFIG _CPD_OFF &_BODEN_OFF &_MCLRE_OFF &_PWRTE_OFF &_WDT_OFF &_XT_OSC

' Registers 76543210
OPTION_REG = %10000000 'GPIO Pull-Ups disabled
INTCON = %00000000 'Set Interrupts
ANSEL = %00000000 'Select analog inputs
WPU = %00000000 'Weak pull-ups (check OPTION_REG)
GPIO = %00000001 'Set PORTS
TRISIO = %00000010 'Set I/Os
CMCON = %00000111 'Comparator Module settings

' Program
MAIN:
SEROUT2 GPIO.0, 813,["TEST",1] '1200bps
PAUSE 00
GOTO MAIN
END


...and the Receiver's code:
' Fuses PIC12F675 - 4MHz XTal
@ __CONFIG _CPD_OFF &_BODEN_OFF &_MCLRE_OFF &_PWRTE_OFF &_WDT_OFF &_XT_OSC

' Registers 76543210
OPTION_REG = %10000000 'GPIO Pull-Ups disabled
INTCON = %00000000 'Set Interrupts
ANSEL = %00000000 'Select analog inputs
WPU = %00000000 'Weak pull-ups (check OPTION_REG)
GPIO = %00000100 'Set PORTS
TRISIO = %00000000 'Set I/Os
CMCON = %00000111 'Comparator Module settings

' Variables
Led VAR BYTE
Led = 0

' Program
MAIN:
SERIN2 GPIO.2, 813,[WAIT("TEST"), DEC1 Led] '1200bps
GPIO.1 = Led
PAUSE 500
GOTO MAIN
END

[tasmod]

Hi Roger and all,

Sorry I've not replied but I'm on a limited internet connection.

Thanks for that info Roger. Unfortunately the site is full of 433MHz stuff already and they are suffering from clashes occasionally, hence 868Mhz requirement.

I believe the Ciseco modules are serial input but transparent modules as well, I'm not sure regarding this, anyone know better ?

They do have a longer range with suitable smaller sized aerials than 433.

His requirement is up to 3km range in semi open environment, point to point. They will be used in parkland with odd tree here and there. I will be able to carry out range tests once finalised and suspect that one yagi and one whip will suffice. If not, two yagis is not out of the question.

They will be in use for just one day occasionally during the year, probably no more than 3 times. They will be temporary and fully portable.

Rob

[tasmod]

Incidentaly, Ciseco claim over 100km range with parabolic antennas, yes 100km.

However they say it probably won't be legal so don't do it. ;-)

[Dick Ivers]

Hi Rob,

I would like to start a project similar to yours. I'm not sure what questions to ask, but just as a beginning here are the project parameters:

Link: One-way communication from a ground based transmitter to an airborne receiver in a flying vehicle.

Range: 3 km minimum line of sight

Frequency: 902 to 928 mhz ISM license free band preferred

Power source: Battery operated on both ends. 3.3 volts doable with regulators.

I looked at the CISECO products and they look good. I think I would choose the ARF high power transceiver on the sending end and the SRF unit for the receiver. The receiver must be very small and light to fit the flight vehicle.

I have considerable experience with PIC programming and printed circuit board development, but no background with wireless stuff. That's the problem and leads to the questions: Where is the documentation on the CISECO products? What's on the vendor's website is sparse to nil. How do I get started?

Dick

[Dick Ivers]

Delete double post

[Dick Ivers]

Hi, The Forum posting was glitching a couple of days ago. My post #15 didn't update the thread to the top of the list. So this is a test to see what happens.

[tasmod]

Hi Dick,

Can't stay on, just to let you know I won't be ordering the modules till this weekend, so I've no info to add.

Try here for many docs Docs (http://www.openmicros.org/index.php/articles/84-xrf-basics)

XRF Datasheet XRF (http://www.openmicros.org/index.php/articles/84-xrf-basics/109-xrf-data-sheet-pdf)

ARF is just a high power XRF, uses same instructions for serial input.

Rob