PicAxe to DORJI DRA886TX, DRA886RX to PC issues

M

Marcwolf

Senior Member
Hi Folks.
I am working on a small project using the DORJI DRA886 modules.

I have the transmitter hooked up to a 28X2 with the simple code

Code: 
main:
serout c.3, T2400_4, ("NNNNNN")
pause 500
goto main
With a scope I can see the square wave output.

So it's very simple. I have a TTL RS-232 hooked up to the DORJI DA886 receiver and inturn via Teraterm

With a scope I can see as square wave output

With Teraterm I am using 2400 baud and various different settings and all I am getting is garbage.

Can anyone offer some advice.


Many thanks
Dave
 
hippy

hippy

Technical Support
Staff member
It is possibly a signal polarity issue between what the receiver puts out and what the TTL RS232 expects.
 
M

Marcwolf

Senior Member
Hi All

I think there must be a 433MHZ transmitter nearby that is blocking my signal.

Hooking the Picaxe directly to the USB serial port I can see the "NNNN" appearing nicely

Doing the same with the receiver but without the picaxe running I just get screens of garbage

Even wiring the two antenna's together does not change a thing. The receiver just free-running garbage.. which is the same when I was trailing another RX/TX combination

Due to space considerations I really need a tiny transmitter because it will be sitting inside my cheek. The receiver will be sitting only an few cm's away on the side of my cheek

Many thanks
Dave
 
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G

Goeytex

Senior Member
Hooking the Picaxe directly to the USB serial port I can see the "NNNN" appearing nicely

Doing the same with the receiver but without the picaxe running I just get screens of garbage
Click to expand...
These ASK receivers will always output a constant stream of noise/garbage unless there is a signal present. When a modulated carrier is present this garbage should turn into discernible data pulses.

Connecting the data output of a receiver to a USB TTL/RS232 Adapter then directly to TeraTerm will not work properly, (if at all). When there is no modulated carrier present, the garbage will be passed to the software. There needs to be a Picaxe between the Receiver and the software to "filter" the output of the Receiver module. This is why they are called "dumb" RF modules. The Picaxe adds a bit of intelligence.

The receiver/Picaxe receives the preamble and qualifier,then the data bytes. Then the Picaxe resends only the pre-qualified data to the PC software.
 
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M

Marcwolf

Senior Member
Hooter said:
You are talking about the cheek on you face I take it?
Click to expand...
Yes - It's a tongue interface that fits into the roof of my mouth. (Prelm photo http://www.marcwolf.org/gallery/?moid=1743)
In my cheek area I have the receiver of this module http://littlebirdelectronics.com/products/wireless-charging-module

With the reciever module sitting within the coil, and a AXE230 and a transmitter module the whole thing is very compact. And also required no wires to be run from the mouth :)

On the outside all I need is the wireless charging transmitter and the DORJI reciever to puck up the signals.

Dave
 
M

Marcwolf

Senior Member
Goeytex said:
These ASK receivers will always output a constant stream of noise/garbage unless there is a signal present. When a modulated carrier is present this garbage should turn into discernible data pulses.

Connecting the data output of a receiver to a USB TTL/RS232 Adapter then directly to TeraTerm will not work properly, (if at all). When there is no modulated carrier present, the garbage will be passed to the software. There needs to be a Picaxe between the Receiver and the software to "filter" the output of the Receiver module. This is why they are called "dumb" RF modules. The Picaxe adds a bit of intelligence.

The receiver/Picaxe receives the preamble and qualifier,then the data bytes. Then the Picaxe resends only the pre-qualified data to the PC software.
Click to expand...
Many thanks.. I will try and set up a picaxe between the reciever and the PC and see if I can see the info.
Dave
 
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