I have a problem, RS232 signal causing interference to audio line, how to solve this problem? did some one experience to solve this? please, share...
thanx.
Obviously nothing to do with Keil software tools!
Are you sure it's the RS232? Conducted, radiated, or what?
Anyhow, you should never run anything digital close to any sensitive analogue signals...
Is your audio well-screened, all you power supplies well-decoupled, etc, etc...?
answers.
yes it is rs232. i think it is radiated but is it conducted? it is well screened.
i use keil for the rs232
"yes it is rs232"
How do you know that?
I mean, how are you certain that it is specifically the RS232 signals that are causing the interference? What tests have you done to confirm it?
"i use keil for the rs232"
No, you use Keil for loading & reading SBUF. Interference between physical signals is entirely a hardware issue - nothing to do with your software development tools!
No, you use Keil for loading & reading SBUF.
not really.
you use your hardware, programmed by Keil for loading & reading SBUF.
Erik
We don't know anything about the environment in which you operate. what kind of equipment are you using? if you are using DC motors, well they tend to draw lots of current as they start turning which might lead to EMC problems. maybe that is the problem? did you try a magnetic shield of some kind?
what is the voltage range of your audio input.
If you run in the millivolts it takes next to nothing to interfere,
It may be that you are confusing "too sensitive" with "too noisy"
also do you have a multilayer board with separate analog and digital ground.
especially if they're high-impedance, unbalanced millivolts.
That's why professional audio uses low-impedance, balanced signals.
And always keep digital well away from sensitive analogue.
Hi,
Get some ferrite rings (the kind that snap around - or wire can be looped through) and that will solve your probs. About 2 or three loops through the ring near BOTH ends of the RS232 cable...
Cheers-Tuvo
Are you sure?
Ferrite rings are effective at radio frequencies - I don't think they'd make any (noticeable) difference at audio frequencies, would they?
I never heard a digital signal disturbing a analog signal when they r on separate lines.
If you think it can,can any one explain me one scenario?
I know that digital signal can cause interference to analog signal when they on a single PCB...because of debouncing effect.
In your case take the grounding measures properly it may work out.
"I never heard a digital signal disturbing a analog signal when they r on separate lines."
Have you never heard the interference caused by a GSM phone placed near to audio equipment?!
The audio output from laptop PCs is renowned for being poor due to interference from all that close-peoximity high-speed digital stuff crammed into such a small space!
It is, in fact, very common indeed - which is why every text on sensitive analogue design will tell you to keep the sensitive analogue signals well away from digital signals. And keep the power supplies well separated.
"If you think it can,can any one explain me one scenario?"
You gave your own example:
"I know that digital signal can cause interference to analog signal when they on a single PCB"
You say you know it happens - why do you need any more examples?!
"because of debouncing effect"
Absolutely nothing whatsoever to do with debouncing!
Maybe "debouncing" is not the right term for what you're thinking of - please exaplain in detail.
"In your case take the grounding measures properly it may work out."
Yes, proper grounding is certainly necessary - though it alone may not be sufficient.
Due to GSM phones interefrence will always be there as they are wireless.
Coming to laptop internally there are tracks on PCBs so intereference will be there.It best explains my point about the interference due to lay outs.
Debouncing mean the signal altering between the ground and transmission line.
But the question was interference between wired signals i want example for that type of scenario....
"But the question was interference between wired signals"
What are PCB traces (tracks) if not "wired signals"?!
The mechanisms of interference between tracks on a PCB are identical to those between signals in cables!
If you place a long microphone cable close to a long mains cable you will get interference between them - in the form of a mains-frequency "hum" on the audio signal. If the mains cable is connected to loads like fluourescent lamps or thyristor dimmers, you will also get all sorts of other nasty noises!
Screening the microphone cable and using low-impedance, balanced signals helps to minimise the susceptibility of the audio to interference...
"Debouncing mean the signal altering between the ground and transmission line."
No - I think you mean "decoupling"?
Or maybe "ground-bounce"?