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Wow nigel i though i would get lost with Manchester scheme but it is pretty straight forward.
Nice tutorial. Ill be sure to print it and use as a reference. I hope if i should fall into some trouble you will be around to help
I have used standard ASCII in RS232 data transmission in telemetry for years with no problems.
I need more info on both. Manchester coding seems easy but i dont like the fact that i have to send "52 bits to send just a single 8 bit data byte" I feel like it asking too much that way. Even tho its more stable still...
If i use UART (ASCII) can i still use that parity bit thing? I never really learned about it. And also like 1 stop bit. You know what i mean?
So what happens when the receiver is out of range, or the transmitter is turned off - and if you're using the hardware UART (without hardware inversion) what happens during a lull in data transmisison? (as wireless links aren't DC coupled).
Are you perhaps using radio links with encoder/decoder built-in?, or ones with modems built-in.
hi,
During normal operation of the link, the RX often loses the carrier, also in certain applications the transmitter is switched off to conserve power while collecting data and powered up to transmit.
The hardware inversion, providing its the same at both ends has no bearing on the problem.
I know telemetry links arent dc coupled I have been using them on a daily basis since the early 1980's, to transmit/receive ascii data, with no problems.
It obvious as I am talking about systems with inbuilt encoders/decoders how else would they work as RS232 data links.? The carrier has to be modulated/demodulated.
Perhaps you should look at the Magenta Radio and Wood and Douglas telemetry system datasheets
Attached a clip from the sparkfun tX data.
EDIT: added this tutorial link for sparkfun
https://www.electro-tech-online.com/custompdfs/2008/08/KLP_Walkthrough-1.pdf
hi Nigel,
I am talking of actual systems that work in the manner I have described.
If you lived closer to me I would take you out for day and show you these systems working.
Read the tutorial that sparkfun have produced regarding the direct connection to a PIC's uart it can't be any plainer than that.
You didn't answer my question though about what happens when the transmitter drops out of range or goes too weak, do you get random rubbish out of the receiver?. If not, why not?
Depends how reliable you want it?
ALL incoming data is verified by the MCU program and if its not valid, its dumped, its standard practice, I thought you would have known, thats why I didnt bother to reply on that point.
As you dont seem to be aware, the same data corruption can occur due to pick up from 'other foreign' transmitters operating close by, thats why ALL telemetry data is verified at the RX by the MCU before being used.
Also TX/RX using Man coding can suffer from this type of corruption, are you saying those MCU's dont valid their data.?
Again, Manchester coding is more robust under those circumstances as well, pretty well all commercial equipment uses it, or something similar.
But preventing it even happening is a better solution.
Manchester is usually used as a packet system, and obviously uses validation of various types - it depends how many bytes per packet you want to use.
May I ask, what practical usage experience have you had in this field.?
Only in using them, and using products which use them - most of which use Manchester coding or similar.
I can only imagine you've only ever used AM units?, and not FM ones, because the way you're using them wouldn't work with FM ones, and suffers from greater problems even with AM ones.
lol im actually enjoying this. You both are good points. I still would prefer to try out the uart since i have some experience with it.
not sure yet. Building one seems trivial.
Tell me if im wrong...
To charge the batteries i have to just supply a certain voltage @ a certain current and it should charge ok?
Of course i would measure the temperature and turn off when too hot.