Or you can capture the pulsetrain with a soundcard and IR receiver for about $1.50Originally Posted by Byte_Butcher
|
Or you can capture the pulsetrain with a soundcard and IR receiver for about $1.50
|
Absolutely! Many different tools to suit your tastes and budget....
I started with a IR receiver (about $1.50) and my old Hitachi scope.
Then I progressed to the IR receiver, stuffed into my soundcard and recorded with Audacity ( http://audacity.sourceforge.net/ ) , which I've used for various signal capture fun for years.
The IR Widget just takes it a step further because the software helps tell you things about a remote that you would otherwise have to calculate or guess at yourself based on recorded scope patterns.
It's just another tool in the box. Use it or not as you please.
steve
|
I am not at the office today so the best I can do (between "honey do" items) is the following for a 12F or 12C series. I think it was posted on rentron.com, this is an example not finished.
Use the inline assembler command in PBP and pop in the code segments that toggle at 38Khz..... you may need to do some massaging though with the code. Use a scope on the data out pin of the IR receiver to make sure your code gives you good solid data output. Do not test RX in close proximity to TX, put your tx out about 10ft or so to make sure even at low signal levels the data makes it through. The analog filters severely reduce signals that are slightly outside of it's center band.
So for every "1" call this in a subroutine with a counter to count 10x through the loop before exiting, for every "0" just pause an equal duration to a "1" for symmetry . If you can... set up your bit duration and start/stop bits so that it is compatible to Serin set for 1200bps on RX side for example....for ease.
Monday I will post 16F code to set the hardware PWM output to 38Khz.
PROCESSOR 12c508
#include "p12c508.inc"
__CONFIG _MCLRE_OFF & _CP_OFF & _WDT_OFF & _IntRC_OSC
#DEFINE PORT B'11111101'
MOVF OSCCAL
MOVLW PORT
TRIS GPIO
BEGIN
BCF GPIO, 1 ;1uS
NOP ;2uS each nop is 1uS long
NOP ;3uS
NOP ;4uS
NOP ;5uS
NOP ;6uS
NOP ;7uS
NOP ;8uS
NOP ;9uS
NOP ;10uS
NOP ;11uS
NOP ;12uS
NOP ;13uS
NOP ;14uS
NOP ;15uS
NOP ;16uS
NOP ;17uS
NOP ;18uS
NOP ;19uS
BSF GPIO, 1 ;1uS Begin HIGH duty cycle
NOP ;2uS
NOP ;3uS
NOP ;4uS
NOP ;5uS
GOTO BEGIN ;2uS (26uS total for 38KHz)
END
|
Need little more of your help :)
Ok then, thanks for all your help upto now. I think I need little more of it.
I have searched the internet and tried to understand the principle behind IR communication. I have made my very first Tx & Rx with that. It's not working as it should do.
It's not a completely dead scenario as I do see voltage fluctuations on the TSOP2438 IR Receiver module output pin when I switch on my transmitter and when I switch my Tx off it goes stable. I also looked into my webcam and could see the IR Tx LED glowing.
I attach my code here to have some feedback on any mistakes I am making. Thanks again.
___________________
WHY things get boring when they work just fine?
|
Do you have an oscilloscope? You have to look at the 38kHz coming out of the TX pin at the pic. You should have 13us high pulse then a 13us low pulse for a period of 26us.
Once you verify the above is happening correctly, then add the code that encodes a "1" bit and a "0" bit. Also IR RX modules do NOT want an IR DC carrier, in other words if you don't modulate at 38Khz with a data burst, shut off the IR LED. So between data transmissions (1 byte or 2 bytes..etc) send data then shut off the IR LED. I have seen many people get stuck on this nasty little characteristic of these devices and waste a lot of time debugging. If you do not the internal capacitive coupled amplifier stages and demodulation stage will charge up with a dc voltage. Within a 1sec to 2 saturate with no more data being demodulated. This is a bad thing.
Make sure that you format your data output based on your transmission speed. If you choose 1200bps then set the bit width (on/off duration) to this spec and don't forget 1 start bit and 1 stop bit for the Debug command at the receiver. It is easy to get caught up in the code and hardware and want to throw all together in one shot. This does not happen until you have done 1or 2 IR projects and discover the pitfalls. My advise, test in pieces.
Below is old TX code using hardware PWM for 16F877A to test IR modules...At the receive side I used Debugin with no other special consideration since the RX module gives me data out. The pause 5 statements need to be tweaked based on your IR module, this delay maybe too short and lead to saturation. I tested this at 40ft no problem very forgiving with the module I used.
INCLUDE "Modedefs.Bas"
@ device HS_OSC, LVP_OFF, WDT_OFF
; @ Device pic16F877A, HS_OSC, BOD_OFF, PWRT_ON, WDT_ON, PROTECT_OFF
DEFINE OSC 20
DEFINE DEBUG_REG PORTC ' point to portB for output
DEFINE DEBUG_BAUD 1200 ' set software TX to 1200 bps
DEFINE DEBUG_BIT 7 ' Set Debug pin bit
DEFINE DEBUG_MODE 0 ' Set Debug mode: 0 = true, 1 = inverted
CCPR1L = 64 ' Set PWM Duty-Cycle to 50%
CCPR2L = 64
PR2 = 128 ' Set PWM for 38.7KHz
CCP1CON = %00001100 ' Mode select = PWM
CCP2CON = %00001100
T2CON = %00000100 ' %00000100 = TMR2 ON 1:1 pre-scale
' %00000101 = TMR2 ON 1:4 pre-scale
' %00000110 = TMR2 ON 1:16 pre-scale
;set ports to output
TRISA = %00000000
TRISB = %00001111
TRISC = %00000000
TRISD = %00000000
; analog portA direction
ADCON1 = 7
CMCON = 7
portc.7=1 ; used to reverse bias LED to shut it off when direct driven (no transistor)
main:
if portb.1 = 0 then
debug 255, 50 ; left
pause 5
portc.7 = 1 ; used to reverse bias LED to shut it off when direct driven (no transistor)
goto main
endif
if portb.2 =0 then
debug 255, 10 ; right
pause 5
portc.7 =1
goto main
endif
if portb.3 = 0 then ; straight
debug 255, 100
pause 5
portc.7 = 1
goto main
endif
; The stop command is sent two times per loop to make sure the RX shuts off
debug 255, 0 ; stop
portc.7 = 1
pause 30
debug 255, 0 ; stop
portc.7 = 1
goto main
Last edited by Macgman2000; - 10th November 2009 at 23:22.
|
Thanks for the reply. Your code surely is good but I don't have 16F877A and neither I am advance enough to use PWM technique at this stage and also even if I think about doing it that way my 12F635 does not have this feature.
"Do you have an oscilloscope?" - No, don't have access to one either. But the LED flashing part of the code is from a trusted source so 40kHz should not be a problem.
Now, with the code I have attached, can you see any obvious mistakes in it?
I know I am using 38kHz receiver BUT transmitting at 40kHz. It is because firstly, I have seen and read that this combination still works if you don't have access to a 40kHz IR Module and secondly, I don't have any knowledge about Assembly so thanks to Bruce @ Rentron (link: http://www.rentron.com/PicBasic/IR_Chips.htm) where I could get this piece of assembly code and stick it in my code as a module and modify my code for 12F635 and send 16 bits instead of 13.
Last edited by financecatalyst; - 10th November 2009 at 23:54.
___________________
WHY things get boring when they work just fine?
Members who have read this thread : 0You do not have permission to view the list of names.
Posting Permissions
Bookmarks