40KHz? Are you receiving me?

[CumQuaT]

Hi everyone,

Has anyone used a PIC (coded with PicBasic Pro) to accurately receive a 40KHz infrared signal before? I'm not sure wether it is do-able or not, so I figured I'd ask you fine people to see if anyone's done it before and if so, what would the code be?

Just to give more info on what I'm doing, the signal I'm trying to receive is as follows:

3ms on
6ms off
3ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on
2ms off
1ms on

So yeah, any help would be awesome. Thanks.

[DaveC3]

Here is a IR remote code I used way back for a Remote Robot using a Sony remote control.



Hope it helps

define  LOADER_USED 1


DEFINE  OSC 20
start:
	ADCON1 = 7 
    'angleVar VAR BYTE	' set up constants with the minimum and maximum pulsewidths
	'SERVO1 CON 450
	'SERVO2 CON 1000	' set up a constant with the time between pulses:
	refreshPeriod CON 20
	A  VAR BYTE	' set an initial pulsewidth:
	'angleVar = minAngle
    TRISB = 0
    TRISA = %00000100
    P_VAL VAR WORD
    IR_DEV  VAR BYTE
    IR_BUT  VAR BYTE
    HEADER  VAR WORD
    BITCNT  VAR BYTE
    PACKET  VAR WORD
    DIRINF  VAR BYTE
    
    SEROUT2 PORTC.6,32,["START  " , 10,13]
main:
	GOSUB IRIN
    SELECT CASE IR_BUT
    CASE $10
    GOSUB LEFT
    CASE $11
    GOSUB RIGHT
    CASE $12
    GOSUB FWD
    
    CASE $13
    GOSUB RE
    
    CASE $14
    GOSUB ST
    
    CASE ELSE
    
    END SELECT
    
 
GoTo main
'Recieve a signel from a Sony remote control
' and return with a 7 bit button code
' IR_BUT and a 5 bit device code IR_DEV in the variable IR_DEV
' if no header then IR_DEV and IR_BUT hold 255

IRIN:   IR_DEV = 255:IR_BUT = 255
        PULSIN PORTA.2,0,HEADER 'Measure header 
        IF HEADER < 1000 THEN RETURN
        IF HEADER > 1350 THEN RETURN ' VERIFY GOOD HEADER IF BAD RETURN
        FOR BITCNT = 0 TO 11
            PULSIN PORTA.2,0,P_VAL
            IF p_VAL >= 450 THEN
                PACKET.0[BITCNT] = 1
                ELSE
                PACKET.0[BITCNT] = 0
            ENDIF
        NEXT
        'Split the 7 bit button code and the 5 bit device code
        IR_BUT = PACKET & %01111111
       
        IR_DEV = (PACKET>>7) & %00011111
        SEROUT2 PORTC.6,32,["BUTTON =", HEX IR_BUT, 10,13]
RETURN


FWD:
FOR A = 1 TO 20
	Low PORTB.7
	Low PORTB.6
 ' pulse the pin
	PulsOut PORTB.7, 450
	PulsOut PORTB.6, 1000
 ' pause for as long as needed:
	Pause refreshPeriod
NEXT A

RETURN

RE:
FOR A = 1 TO 20
	Low PORTB.7
	Low PORTB.6
 ' pulse the pin
	PulsOut PORTB.7, 1000
	PulsOut PORTB.6, 450
 ' pause for as long as needed:
	Pause refreshPeriod
 NEXT A
RETURN
ST:
Low PORTB.7
Low PORTB.6
'PAUSE 1000
RETURN

LEFT:
FOR A = 1 TO 20
	Low PORTB.7
	Low PORTB.6
 ' pulse the pin
	PulsOut PORTB.7, 1000
	PulsOut PORTB.6, 1000
 ' pause for as long as needed:
	Pause refreshPeriod
 NEXT A
RETURN


RIGHT:
FOR A = 1 TO 20
	Low PORTB.7
	Low PORTB.6
 ' pulse the pin
	PulsOut PORTB.7, 450
	PulsOut PORTB.6, 450
 ' pause for as long as needed:
	Pause refreshPeriod
 NEXT A
RETURN

[Kamikaze47]

You should be able to use the PULSIN command to measure the length of the pulses, but we will need more info to give further help.

I assume you have an IR receiver hooked up to one of your I/O pins?

Is the IR signal coming from a remote control? If so, what is the remote for, and what brand is it? Do you know the encoding scheme its using?

[comwarrior]

ET phone home?

[ardhuru]

From the figures you have given, it looks like the modulation frequency might be 40 kHz; the actual data is slower. So, as long as your IR receiver module can handle 40 kHz, decoding the data (pulse widths and spaces), which is in milli seconds, should most certainly be within the scope of PBP.

Depending on the range you expect, even a generic 36 - 38 kHz IR module should work fine at 40 kHz.

Anand

[CumQuaT]

Hi all,

Thanks for the responses. Sorry it takes me so long to respond. I'm in Australia, so with the time differences all of your responses come in while I'm asleep.

I'm using a 40KHz phototransistor to receive, yes, and interfacing it to a PIC16F628A oscillating at 4MHz.

Thanks for the example code, DaveC3. It's not a remote control that I'm trying to read from, but I imagine it's a similar process across the board. I'll pick that code apart and see what I can come up with.