> -----Original Message----- > From: Andrew Seddon [SMTP:seddona@HOTMAIL.COM] > Sent: Friday, April 14, 2000 12:41 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: [EE]:Telemetry encoding > > ----- Original Message ----- > From: Jilles Oldenbeuving > To: > Sent: Wednesday, June 14, 2000 11:03 PM > Subject: Re: [EE]:Telemetry encoding > > > > Actually, i'm busy with it too right now! (Let's start a Telemetry > encoding > > list ) > > Only, i'm decideing at the moment wich radio module to use... I've got > some > > parts from Quasar (www.quasar-ltd.com) and RF Solutions. Didn't buy any > > Radiometrix modules, becouse the price is to high for my mid-quantity > > application. > > Anybody has some good suggestions on what to use? > > > > I've also looked at the radiometrix site at that info you're talking > about. > > What scheme will > > you be useing for the telemtry encodeing? (or what scheme's have others > > used with succes?) I think one also has to implement a CRC-check. For > my > > testing purposes i'd thought about the summing-check (just sum all the > data > > you want to send, without respect to the carry bit). But after diving > into > > the > > matter more closely i'd say one has to use a real CRC-check (dividing > the > > data with a "poly", or whatever). I'm not sure how i could treat the 6 > > databytes > > i want to send as a long series of bits wich will be devided by the poly > in > > an > > effecient way..... > > > > > > I`m not sure about the modules that you are using but the radiometrix ones > work best on a 50:50 mark space ratio. I think you would probably get > better > data rates if your error checking scheme tried to maintain this.. Possibly > using a parity bit to make each byte 50:50?? Not really sure, when I have > sorted mine I will post some code. > A single parity bit (per byte) won't help you acheive a balanced 1/0 ratio. Probably the most simple method is to use Manchester encoding where each bit is sent as a 0/1 or 1/0 transistion, ensuring a balanced bit stream. This does of course use twice the bandwidth of simple NRZ encoding. Another way is make the system packet based, and have your packet controller pad out the packets to ensure a balanced bit stream. How large/small the packets can be made depends on the bit rate and the maximum 1 or 0 time that the radio system can reliably transmit/receive. I believe Radiometric actually sell a packet controller which takes care of all this. Mike