12f675_fuse_about_to_blow!

[LEDave]

update:

I've just ordered up the 433MHZ transmitter and receiver modules.

Dave

[LEDave]

Questions:

1/ If you had two circuits, or more to the point two 433MHZ receivers in close proximity, would one transmitter interfere with or trigger both receivers?

2/ If the answer to Q1 is yes, is there anyway (either by software or physically) to slightly change a transmitter and receivers operating frequency to make them totally independent units?

Dave

[mackrackit]

Q1 is yes.

Some modules can be set a little off frequency but most "hobby" types can not. I do not know if the RFPICS can be.

There are also encoder/decoder chips.

But I will say "normally" it is done in software.
Basically think of a computer network. Each device has an address.
If the packet does not have your address attached then the packet is ignored.

[LEDave]

But I will say "normally" it is done in software.
Basically think of a computer network. Each device has an address.
If the packet does not have your address attached then the packet is ignored.

Cheers mackrackit, so it should be possible to send data only to a designated receiver module?

There is a reason I'm asking this.....Another project

The modules have been shipped today (very efficient I must say).

Dave

[mackrackit]

so it should be possible to send data only to a designated receiver module?

Yes and no...
When data is sent it is sent everywhere. It is up to the receiver to "decode" the signal. Even data that the receiver does not understand hits the receiver.

Think back to serial comms with wires. You have a "wait" for something before the receiver acts on the data. Pretty much the same with RF. But with RF there is noise from everywhere hitting the receiver.

Dig through the app notes from these folks
http://www.linxtechnologies.com/Supp...ication-Notes/
AN-00160
AN-00232
AN-00500
AN-00501
Are some good one to start with.

[LEDave]

Dig through the app notes from these folks

Will do mackrackit, thanks for the info. My RF knowledge is less than my LED knowledge when I first came here right now......oh dear.

The Modules arrived today (I only ordered them yesterday) they came over from Belgium too. They are quite small (I was expecting them to be larger, I don't know why). I'll have a closer look when I get a minute / tonight.

RF is the 'Holy Grail' for me. If I can figure this one out then it's uses are nigh on endless.

Dave

[LEDave]

mackrackit,

Those notes are really interesting and informative, I'm working my way through them, cheers.

Dave

[mackrackit]

Next you will want to get a HAM licence

[LEDave]

Next you will want to get a HAM licence

Mmm............

[LEDave]

Problem?:

I'm thinking I should have ordered the: "rfPIC software and complete documentation (on CD)"?

There was no CD in either of the boxes. I'm thinking I'm up the creek without it? Or can I get by without the CD?

Sorry I know, more questions.

Dave

[mackrackit]

This might be a place to start
http://www.farnell.com/datasheets/309975.pdf

I have not used the rfPIC modules but I think we can figure it out.

A quick look at the data sheet.
Header J3 in the PICKIT1 needs to be used after removing the chip from the evaluation socket. My PICKIT1 just has holes for J3, if yours is that way you will need to bring wire off it to a bread board. Looks like J3 pin#1 is on the edge of the board.

Then after the module is programed it should be able to "stand alone" on the bread board.

[LEDave]

Hi mackrackit

This might be a place to start
http://www.farnell.com/datasheets/309975.pdf

Absolutely, I tracked down the Microchip.pdf (same one I think) anyway my PICkit1 does have header J3 on it, so that's a help.

I spent ages last night mulling over how all this might work and it seemed to me that I either:

1/ I need two PICkit1 boards one for the TX and one for the RX.

2/ The TX is 'stand_alone' with a battery fitted - However, the TX has a socket for a 12F675 (you have to break some tracks for this to work I think) So I'm not sure if the TX will work without the 12F675 and tracks broken in some kind of test mode (if that makes sense). Or will only work as 'stand_alone' with a program loaded into the 12F675 and tracks broken.

Dave

[mackrackit]

Both modules are stand alone. The 8 pin socket on the transmitter is optional. I would not cut anything at the moment.

It is my understanding that the rfPIC12F675 is just a 12F675 with RF on board, plugging the modules into the PICKIT1 is just a way to program them.

I bet the software for the PICKIT1 sees the modules as is. Have you plugged either one into the PICKIT1 yet?

One the modules are programed you should be able to power them with out the programmer attached.

Maybe...

[LEDave]

Both modules are stand alone. The 8 pin socket on the transmitter is optional. I would not cut anything at the moment.

Really pleased to not have to cut the tracks, I was dreading that job!

I bet the software for the PICKIT1 sees the modules as is. Have you plugged either one into the PICKIT1 yet?

No I haven't plugged either into the PICkit1 as yet. The TX has a battery holder for a round CR2032 battery (which I don't have), I'm thinking if I got one of these (tomorrow) for the TX and plugged the RX into the PICkit1 we have two fully powered TX_RX circuits. How does that sound?

Dave

[mackrackit]

That should work.
It also looks like it you leave the program power jumper on you should be able to power the transmitter while in a breadbord from any 2 to 5 volt source.
Not sure how long the coin battery will last.

[LEDave]

It also looks like it you leave the program power jumper on you should be able to power the transmitter while in a breadbord from any 2 to 5 volt source.

I saw that, very handy. It would be good to buy a few expansion headers (J3) as well if I can source them, rather than solder the actual modules onto a vero board.The TX module won't push into my breadboard either (a real shame that) as the pins lie flat against the circuit board, again a J2 header would have solved that, never mind.

I'm so keen to try these modules out that I've been seriously thinking of soldering the TX module to a vero board and running a power supply to it but after a rush of blood I've decided to get the battery tomorrow and have TX stand alone using the battery and RX in the PITkit1.

Roll on tomorrow.

Dave

PS: The Badger hasn't made an appearance for three nights in a row now, we're a little worried for him....

[LEDave]

I've bought a 3v battery for the TX and fitted it, a red LED blinks when either push button switch 1 or 2 is pressed, so seems to be working.

As for the the RX module (I haven't inserted this yet), the evaluation socket is empty and the PIC16C745 Firmware chip is still in place. I'm tempted to insert the RX module into the J3 Header but haven't.

Not sure what to do next.

Dave

[LEDave]

This is what microchip has to say:

http://ww1.microchip.com/downloads/e...Doc/70092a.pdf

1.3 GETTING STARTED WITH THE rfPIC DEVELOPMENT KIT 1
The transmitter modules come pre-programmed with a transmitter demonstration. The
enclosed PIC16F676 is programmed with a receiver demonstration program. Together
they demonstrate an on-off command and control application.
The PICkit 1 FLASH Starter Kit serves as a low-cost development and demonstration
platform for the transmitter and receiver modules.
To see your rfPIC Development Kit 1 in action, perform the following steps:
1.3.1 Preparing the Receiver Module for Operation
Step 1:
Familiarize yourself with the PICkit 1 FLASH Starter Kit operation by reading the
PICkit™ 1 FLASH Starter Kit User’s Guide (DS40051) and performing some of the
tutorials. Familiarity with the PICkit Starter Kit will be assumed throughout this user’s
guide.
Step 2:
Remove power from the PICkit Starter Kit by disconnecting the USB cable.
Step 3:
Remove the PIC12F675 from the PICkit Starter Kit evaluation socket.
Step 4:
Insert the PIC16F676 into the PICkit Starter Kit evaluation socket. See Figure 1-1.
Step 5:
Insert a receiver module (315 or 433.92 MHz) into the PICkit Starter Kit expansion
header J3. Make certain that the receiver module is oriented correctly. See Figure 1-1.

So it looks to me that if I'd have bought a complete rfpic development kit it would have come with a PIC16F676 programmed with a receiver demonstration program. So the TX has a demo program installed but I haven't got a PIC16F676 for the RX with a demo program.

[mackrackit]

I have not had time to look into this very much but some demo programs can be found here. In ASM though.
http://www.microchip.com/stellent/id...cName=en010060

[LEDave]

Cheers mackrackit,

I'll have a look and a tinker (tinker is that an engineering term...) and report back.

An RF_LED_Blink program would do for me right now.

Dave

[LEDave]

I found this RX_Demo program for the rfpic, only thing is it says 16f675 again, so no joy so far.

Filename: rcvr_demo.asm
; Date: April 25, 2003
; File Version: 1.0
; Assembled using:
;
; Author: Steven Bible
; Company: Microchip Technology Inc.
;
;
;----------------------------------------------------------------------
;
; Files required:
; p16f676.inc

[mackrackit]

Did some more poking around.
If you have not seen these they will be helpful. Data sheets for the actual chip on the modules.
http://ww1.microchip.com/downloads/e...Doc/70090a.pdf
http://ww1.microchip.com/downloads/e...Doc/70091a.pdf

As you know the transmitter is programmable and it appears that both modules are pre configured for ASK modulation.

You can find out more about modulations here.
http://davehouston.net/RFTipsTricks.htm
Dave has a whole lot of good info on his site.
http://davehouston.net/

Looks like you can use pin #11 from the receiver module to connect to any PIC for serial data so the code that Bruce posted can be used.

[LEDave]

Thanks for the info mackrackit, the TX does work, the doorbell has rung several times now when the TX is pressed Still no blinking LED though, will get there though.

Dave

[LEDave]

Well I've spent most of this evening loading demo programs into the TX and RX, and doing a lot of reading, still not a blip or lit LED in sight........

Dave

[LEDave]

I'm thinking I need to go back to my MPLAB IDE and figure out how to convert an Assemler program to a HEX file and load that into my RFPIC TX and RX.

The words Assembly language and Dentist have exactly the same effect on me and I don't like either. The first because I'm not clever enough to understand it fully and the second because I do......

It's a shame there's not a MCS_RF section........Grrr.

Dave

[mackrackit]

Check this out. Bruce to the rescue... Again
He is using a 676 connected to the receiver but you should be able to adapt the receiver code to whatever you have.
http://www.picbasic.co.uk/forum/show...ighlight=rfPIC

[LEDave]

Cheers mackrackit (and Bruce).

I'll have a go over the next day or two and report back.

I've got my first RF project lined up: A friend of mine and a keen clay pigeon shooter wants to be able to fire his clay trap by remote control instead of a long wire. I told him I'll have a go, just give me six Months, he says there's no rush, just as well

Dave

[LEDave]

Hi mackrackit,

I've had a: " Small breakthrough for mankind, a giant breakthrough for me" evening.

I've managed to get the Demo_prog to run. LED's D0 & D1 light when the push buttons are pressed, so very pleased with that.

The TX range was a little on the low side at about 50 yards, 200 would be fantastic. I'm going to make a stand alone receiver board next and see how that goes.

Always good to get something working

Dave

[mackrackit]

COOOOL!!!

Range-- What are you using for an antenna?
1/4 wave (6.5 inches) wire over a ground plane?

[LEDave]

Range-- What are you using for an antenna?

At the moment it's a single wire (AWG 24) approx 6.5" long.

The booklet says: "Alternatively, the pin receptacle can be removed and an alternative antenna connection can be made. For example a coaxial wire can be connected to the antenna pad on the front side of the pcb and ground pad on the back side of the pcb."

Early days yet but would one of these be any better?

http://www.maplin.co.uk/Module.aspx?ModuleNo=35648

Dave

[mackrackit]

For something permanent that would be good, but you still need a ground plane with any 1/4 wave antenna.
For prototyping I use a wire stuck into a bread board with the bread board setting on an aluminum plate. The plate is connected to ground (zero rail).

http://www.arrl.org/files/file/Techn...df/6201025.pdf
http://www.arrl.org/files/file/Techn...20Radiates.pdf

[LEDave]

For something permanent that would be good, but you still need a ground plane with any 1/4 wave antenna.

I remember reading somewhere that for a 1/2 wave antenna you don't need a ground plane, is that an option here?

For prototyping I use a wire stuck into a bread board with the bread board setting on an aluminum plate.

Is the wire then attached to the plate or the RX device?

Dave

[mackrackit]

I remember reading somewhere that for a 1/2 wave antenna you don't need a ground plane, is that an option here?

Yes but it will basically need two 1/4 wave wires. the ground plane sorta takes place of the second wire. 1/2 wave has advantages but for a portable the 1/4 wave is the most practical.

Is the wire then attached to the plate or the RX device?

The wire is the 6.5 inch antenna.
Using the above setup I can get .5 mile line of site with these.
http://www.rentron.com/remote_control/TWS-434.htm
http://www.rentron.com/remote_control/RWS-434.htm

[LEDave]

I see, does it have to be an aluminium plate or would a good size piece of vero board be ok.

I liked those RENTRON TX_RX modules, I don't think for one moment they'd ship to the UK? Probably cost too much in postage, then again the module price was excellent.

Dave

[mackrackit]

I see, does it have to be an aluminium plate or would a good size piece of vero board be ok.

Has to be electrically conductive.
Probably find something in the kitchen that would work....

[LEDave]

Probably find something in the kitchen that would work....

I've just tried a small aluminium vice from the shed and an aluminium tray (from the kitchen funnily enough ) the vice added another 5 - 10 yards, the tray not so much. I had a few funny looks from the neighbours every time I waved back at Mrs LEDave to say an LED had blinked as I walked up the street.

I'm sure the distance can be boosted with some more tweaking.

Dave

[mackrackit]

I had a few funny looks from the neighbours

My neighbors moved...

The antenna is half of the radio. It is the one part that is easy to tweek.
If you really want to get into antennas the arrl.org site has a ton of info. I keep the ARRL Antenna Handbook close. About as bad as a data sheet though, 900+ pages of good info.

[LEDave]

My neighbors moved

Lol.....

Well I'm just after a couple of hundred metres, I'm sure we'll get there.Thanks for the antenna link.

My neighbors moved

Cracking.

[LEDave]

I'm having problems compiling Bruce's program and I keep getting the two error messages below:

Found label after column 1 (Device) Illegal opcode PIC16F676) & Illegal opcode (PWRT_ON)

I had this once before with one of my programs, it turned out I had the wrong PIC selected from the drop down list but I haven't this time.

Any ideas?

Dave

[ScaleRobotics]

It does not like the way configs were defined:

@ DEVICE PIC12F675,MCLR_OFF,INTRC_OSC_NOCLKOUT,WDT_OFF,BOD_OFF
@ DEVICE PWRT_ON,PROTECT_OFF

And some of the names of the registers needed some "E" 's added to them.

Try this instead:

@ __CONFIG _MCLRE_OFF & _INTRC_OSC_NOCLKOUT & _WDT_OFF & _BODEN_OFF & _PWRTE_ON & _CP_OFF

Walter