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Author Topic: What is manchester code  (Read 9791 times)
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arash
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« on: December 06, 2005, 04:17:24 16:17 »

Hi all
Do you know What is manchester code.
(It is in Mikrobasic)
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Wizpic
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« Reply #1 on: December 06, 2005, 08:35:18 20:35 »

it's what you use sending data over RF, the transmitter side encodes it sends it over RF and the reciever decodes it. it's the best way to do RF. RF stuff is very hard to do the best thing you can do if you want to find out more is go here
 
http://www.picbasic.co.uk/forum/showthread.php?t=198&highlight=manchester
 
theres quite a bit of stuff on it. the trouble you will find is that prople who got it working will not share as they can work very hard to get it working and error free
 
hope this helps
 
wizpic
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meax98
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« Reply #2 on: December 07, 2005, 10:35:55 10:35 »

Manchester code is a code in which data and clock signals are combined to form a single selfsynchronizing data stream. Each encoded bit contains a transition at the midpoint of a bit period, the direction of transition determines whether the bit is a 0 or a 1. Second half is the true bit value and the first half is the complement of the true bit value.
 
Manchester RF_Send_Byte format
St1 St2 Ctr B7 B6 B5 B4 B3 B2 B1 B0
[/size][/font]
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arash
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« Reply #3 on: December 07, 2005, 12:44:46 12:44 »

It realy hard to understand. Do you have a sample?
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meax98
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« Reply #4 on: December 07, 2005, 02:13:43 14:13 »

No, it's not hard. You are using mE mikroBasic, as I can see:
 
This is "transmit" part:
program RF_TX
dim i as byte
dim msg as string[20]
main:
msg = "mikroElektronika"
PORTB = 0 ' Initialize port
TRISB = %00001110
ClearBit(INTCON, GIE) ' Disable interrupts
Man_Send_Init(PORTB) ' Initialize Manchester sender
while TRUE
Man_Send($0B) ' Send start marker
Delay_ms(100) ' Wait for a while
for i = 1 to Strlen(msg)
Man_Send(msg) ' Send char
Delay_ms(90)
next i
Man_Send($0E) ' Send end marker
Delay_ms(1000)
wend
end.
This is "receive" part:
 
program RRX
dim error, ErrorCount, temp as byte
main:
ErrorCount = 0
TRISB = 0
CMCON = 7
' VRCON = 0 ' Uncomment the line for PIC16
Lcd_Init(PortB) ' Initialize LCD on PORTB
Lcd_Cmd(LCD_CLEAR)
Man_Receive_Config(PORTA,3) ' Configure and synchronize receiver
while true
Lcd_Cmd(LCD_FIRST_ROW)
while true ' Wait for the start marker
temp = Man_Receive(error)
if temp = $0B then
break
end if ' We got the starting sequence
if error then ' Exit so we do not loop forever
break
end if
wend
do
temp = Man_Receive(error) ' Attempt byte receive
if error = true then
Lcd_Chr_Cp(63) ' ASCII for "?"
Inc(ErrorCount)
if ErrorCount > 20 then
Man_Receive_Init(PORTA)
' alternative:
' temp = Man_Synchro
ErrorCount = 0
end if
else
if temp <> $0E then ' Don't write the end marker on LCD
Lcd_Chr_Cp(temp)
end if
Delay_ms(20)
end if
loop until temp = $0E ' Wait for the end marker
wend
end.
 
Hardware: 2 x PIC16F877A (with OSC 4 MHz), pair of RX/TX modules
- on TX module connect DATA_IN pin to RB0 of TX PIC
- on RX module connect DATA_OUT pin to RD6 of RX PIC
« Last Edit: December 07, 2005, 02:18:59 14:18 by meax98 » Logged
arash
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« Reply #5 on: December 07, 2005, 07:30:16 19:30 »

Thank you.this can realy help me.But what is the hardware.Sorry i'm a little dimwit..
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Wizpic
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« Reply #6 on: December 08, 2005, 01:11:21 01:11 »

your 2 pic chips and RF unit that make it work with out these you may aswell not bother writing code
 
it would be like you trying to drive a toy car
 
wizpic
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« Reply #7 on: December 08, 2005, 06:52:16 06:52 »

What's the detail of RT4 and RR3?
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« Reply #8 on: December 08, 2005, 08:56:40 08:56 »

In my experience, no need to get too detail with these boards.  They just works.  Factory pretuned and pre aligned make these BFM (Bloody Fukn Magic) boards a breeze to use.Cheesy

Just treat the  RF boards as component, why bother to find out whats inside a PIC chip? Just use them as the specs suggested.Wink  

You could buy those or their similar variant from Mouser, Digikey, Australian Oatley Electronics etc.  There should be datasheets from them seller's site. :p
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meax98
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« Reply #9 on: December 08, 2005, 09:30:35 09:30 »

Here is explanation for TX/RX modules.
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arash
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« Reply #10 on: December 08, 2005, 09:59:57 21:59 »

What do you mean Parmin?I must connect an ant to the output pin.Is that enough?
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Parmin
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« Reply #11 on: December 09, 2005, 07:26:10 07:26 »

Yup.  Connect a 1/8 wavelength cable at the output and tadaaa......  Although 1/4 or 1/2 length give better distance.
 
1/8 wavelenth is about 180 mm err... 7 inch?
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jugglerb
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« Reply #12 on: December 09, 2005, 03:24:53 15:24 »

if you happen to turn the tuning screw how easy is it to get these re-tuned?
I moved mine - is the tuning vital or is this just a fine tune mechanism?
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meax98
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« Reply #13 on: December 09, 2005, 04:44:50 16:44 »

It's very easy to re-tune them. Make small circuit for TX part (very simple, button, TX module, something to produce data stream) and also for TX part (RX module, LED) and have fun. With that "tuning screw" you are "changing" channels.
« Last Edit: December 10, 2005, 03:36:21 15:36 by meax98 » Logged
Parmin
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« Reply #14 on: December 10, 2005, 01:25:31 01:25 »

at 433 Mhz, a nudge would bring you up ur down a few hundred khz.  Bad news.
 
To re tune do as Meax98 said.  Hookup an LED on output of the RX, then tx something out and tune till the LED is the brightest... should get ye within a few tens Khz.  Unless you have a freq counter, you may not be able to better that.
 
Make sure you use the original freq coz if you change them and have to replace them boards (coz it got zap or sum'pin'?) you would have to go to all the tuning drama again.
 
Make sure you tune them with non metalic tool so the freq do not drift.
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meax98
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« Reply #15 on: December 10, 2005, 03:35:28 15:35 »

jugglerb, btw, why did you play with the "tuning screw"?. What did you try to achieve?
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nileshhande
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« Reply #16 on: October 20, 2006, 07:54:02 19:54 »

No, it's not hard. You are using mE mikroBasic, as I can see:
 
This is "transmit" part:
program RF_TX
dim i as byte
dim msg as string[20]
main:
msg = "mikroElektronika"
PORTB = 0 ' Initialize port
TRISB = %00001110
ClearBit(INTCON, GIE) ' Disable interrupts
Man_Send_Init(PORTB) ' Initialize Manchester sender
while TRUE
Man_Send($0B) ' Send start marker
Delay_ms(100) ' Wait for a while
for i = 1 to Strlen(msg)
Man_Send(msg) ' Send char
Delay_ms(90)
next i
Man_Send($0E) ' Send end marker
Delay_ms(1000)
wend
end.
This is "receive" part:
 
program RRX
dim error, ErrorCount, temp as byte
main:
ErrorCount = 0
TRISB = 0
CMCON = 7
' VRCON = 0 ' Uncomment the line for PIC16
Lcd_Init(PortB) ' Initialize LCD on PORTB
Lcd_Cmd(LCD_CLEAR)
Man_Receive_Config(PORTA,3) ' Configure and synchronize receiver
while true
Lcd_Cmd(LCD_FIRST_ROW)
while true ' Wait for the start marker
temp = Man_Receive(error)
if temp = $0B then
break
end if ' We got the starting sequence
if error then ' Exit so we do not loop forever
break
end if
wend
do
temp = Man_Receive(error) ' Attempt byte receive
if error = true then
Lcd_Chr_Cp(63) ' ASCII for "?"
Inc(ErrorCount)
if ErrorCount > 20 then
Man_Receive_Init(PORTA)
' alternative:
' temp = Man_Synchro
ErrorCount = 0
end if
else
if temp <> $0E then ' Don't write the end marker on LCD
Lcd_Chr_Cp(temp)
end if
Delay_ms(20)
end if
loop until temp = $0E ' Wait for the end marker
wend
end.
 
Hardware: 2 x PIC16F877A (with OSC 4 MHz), pair of RX/TX modules
- on TX module connect DATA_IN pin to RB0 of TX PIC
- on RX module connect DATA_OUT pin to RD6 of RX PIC


hi,
could you please explain above code for toggle bit and momentry ...

THANKING YOU,

WARM REGARDS,

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arturo10422
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« Reply #17 on: April 08, 2008, 12:28:26 12:28 »

I need to know boud rate of data trasfer
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billy77
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« Reply #18 on: April 09, 2008, 01:00:30 13:00 »

340 ~ 560 bps
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« Reply #19 on: April 13, 2008, 08:49:18 08:49 »

Manchester encoding is a synchronous technique used alot in the early days of "PCs" (the 70's & 80's) by builders of offline storage interfaces like cassette tape and reel-to-reel mag devices, since it is relatively immune to single-bit error.

Atari, IMSAI, SOL Technologies, Commodore, and Altair ALL had Manchester NRZ encoded storage devices...

For more info read the page at: http://www.erg.abdn.ac.uk/users/gorry/course/phy-pages/man.html

Cheers-Tuvo

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« Last Edit: April 14, 2008, 03:22:58 03:22 by tuvoj » Logged
goslock
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« Reply #20 on: April 14, 2008, 06:16:30 06:16 »

Quote
it's what you use sending data over RF, the transmitter side encodes it sends it over RF and the reciever decodes it. it's the best way to do RF. RF stuff is very hard to do the best thing you can do if you want to find out more is go here
 
http://www.picbasic.co.uk/forum/showthread.php?t=198&highlight=manchester
 
theres quite a bit of stuff on it. the trouble you will find is that prople who got it working will not share as they can work very hard to get it working and error free
 
hope this helps
 
wizpic

   
I think the best option to make the code manchester
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« Reply #21 on: April 16, 2008, 07:45:29 07:45 »


/shrug

Manchester Encoding is certainly not as complicated as people seem to want to believe it is.

Melanie quote's Manchester's simplicity in one easy paragraph
Quote
Here is the secret of Manchester encoding/decoding in all it's simplicity... (in case any other reader wants to know why - it's to balance the data slicer in the receiver and help cancel out noise).

Encoding: 8 bit byte becomes 16 bits to transmit... zero's become "01" and ones become "10".

Decoding: 16 bits get deconstructed back to 8 bit byte... "01" gets turned back into a zero and "10" gets turned back into a one.

Example... you are sending byte $00 which is equal to %00000000... this get's turned into %0101010101010101.

Melanie




Summary:

  • Each bit is transmitted in a fixed time (the "period").
  • A 0 is expressed by a low-to-high transition, a 1 by high-to-low transition (according to G.E. Thomas' convention -- in the IEEE 802.3 convention, the reverse is true).
  • The transitions which signify 0 or 1 occur at the midpoint of a period.
  • Transitions at the start of a period are overhead and don't signify data.

Manchester code always has a transition at the middle of each bit period and may (depending on the information to be transmitted) have a transition at the start of the period also. The direction of the mid-bit transition indicates the data. Transitions at the period boundaries do not carry information. They exist only to place the signal in the correct state to allow the mid-bit transition. Although this allows the signal to be self-clocking, it doubles the bandwidth requirement compared to NRZ coding schemes

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DINESHjp
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« Reply #22 on: August 23, 2008, 03:25:22 03:25 »

has someone tries the sample program of mikrobasic  i think it wont work
if anybody has successfully run that, plz share the experience
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« Reply #23 on: August 23, 2008, 09:12:49 21:12 »

has someone tries the sample program of mikrobasic  i think it wont work
if anybody has successfully run that, plz share the experience
If you had read Wizpic's link, http://www.sonsivri.com/forum/index.php?topic=480.msg2121#msg2121
 it shows error in posted code. and you will find working code, that only needs a small amount of work, to get up to speed with manchester code.
Melanie has posted a load of working code. they even call it Melbasic [sic] after her Smiley
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« Reply #24 on: August 23, 2008, 09:34:17 21:34 »

has  someone  implemented  in FLOWCODE?,  let me  know how  we  could  do this  in that program .thanks ahead
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