IR Comm Issue

Comments

• thTechie Posts: 7

  2012-01-02 01:35 edited 2012-01-02 01:35

  I've been doing a bit more work on this and still can't get anything to happen that makes any sense. I've cut out all the rest of the code to try to isolate the problem, but no luck so far. Below is my code and what it's outputting.
  

  CON
  
    _clkmode = xtal1 + pll16x
    _xinfreq = 5_000_000
  
  OBJ
  
    IROut:   "jm_irtxserial"
    IRIn:    "FullDuplexSerial"
    Comp:    "Parallax Serial Terminal"
  
  DAT
  
    stack        long 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0   'Stack space
    PlayNoPt     long 0
    PlayNo       byte %11010100
  
  PUB main
  
    PlayNoPt := @PlayNo
    
    Comp.start(115200)
    Comp.bin(byte[PlayNoPt], 8)
    Comp.NewLine
  
    dira[11] := 1
    dira[12] := 0
    if (cognew(IRMont, @stack) + 1) == 0
      Comp.str(String("Error! Can't start IR Mon"))
      
  
    repeat
      if IROut.Start(2_066_953, 11, 2400) == 0
        Comp.str(string("Cannot Start IR Send Cog!"))
      waitcnt(clkfreq/200 + cnt)
      
      IROut.bin(byte[PlayNoPt], 8)
      IROut.stop
      waitcnt(clkfreq * 2 + cnt)
       
  PUB IRMont | rxByte
  
    dira[12] := 0
    IRIn.start(12, 27, %0000, 2400)
    
    repeat
      rxByte := IRIn.rxcheck 
      if rxByte <> -1
        Comp.bin(rxByte, 8)
        Comp.NewLine            
  

  
  Output:

  11010100 (note: this is what I'm attempting to send, the following lines is what it's receiving)
  00000011
  11111100
  00000011
  11111100
  00000011
  11111100
  00010011
  11111100
  00000011
  11111100
  00000011
  11111100
  00100011
  11111100
  00001011
  11111100
  00000011
  11111100
  00000011
  11111100
  

  
  Any thoughts, suggestions, places to look, or just anything really would be VERY much appreciated!
  
  Thanks,
  Kenny
• MagIO2 Posts: 2,243

  2012-01-02 03:18 edited 2012-01-02 03:18

  If I read Jonny's code right he is modulating the output. This is common for IR transmissions like remote controls do it. So, do you have a demodulator connected to the receiving pin? A IR photo-diode alone will not work!
  
  The demodulated signal will then look like a common serial signal and can be fed into the receiving-pin!
• JonnyMac Posts: 9,376

  2012-01-02 11:22 edited 2012-01-02 11:22

  So, do you have a demodulator connected to the receiving pin?

  
  MagIO2 is correct: you need a demodulator on the RX side. This one will work:
  -- http://www.parallax.com/Store/Components/Optoelectronics/tabid/152/CategoryID/30/List/0/SortField/0/Level/a/ProductID/177/Default.aspx
• thTechie Posts: 7

  2012-01-02 13:55 edited 2012-01-02 13:55

  Sorry guys, I suppose I also should have included how its hooked up. I've got an IR LED connected to pin 11 with a 100 ohm resistor in series. On pin 12 I've got the it receiver that comes with the PEK (which I believe is the same one that you linked to) through a 4.7k ohm resistor. I also know for sure that led is working because I can see it on my phone's camera.
  
  Thanks again,
  Kenny
• MagIO2 Posts: 2,243

  2012-01-02 23:13 edited 2012-01-02 23:13

  Ok ... just wanted to make sure ;o)
  
  Next guess:
  mov txBitCount, #11 ' start + 8 data + 2 stop
  
  This is part of jm_irtxserial.spin. Do you have the same settings on input-side? I think 2 stop-bits is not very common. (I don't have the Parallax Serial Terminal sources at hand, so you have to verify this by yourself)
  
  But having a closer look something is very obvious:
  
  IROut.bin(byte[PlayNoPt], 8)
  here you do not send one byte, you send 8 bytes which are equal to the string "11010100" - one ascii-byte for each character.
  
  rxByte := IRIn.rxcheck
  here you receive the string byte by byte
  
  Comp.bin(rxByte, 8)
  and here you output one byte again as a binary string.
  
  So, I think together with the wrong stop-bit-settings you get your wrong output.
  
  
  To fix the send/receive-discrepancy you have 2 options:
  1. change send-part to use IROut.tx instead of IROut.bin
  2. change receive-part to Comp.tx instead of Comp.bin
  
  It depends on what you want to achieve with your program. In 1. you have the binary data at receiver-side and you can easily use the byte there. In 2. the protocol is human readable but needs to send 8 characters per byte.
• thTechie Posts: 7

  2012-01-03 00:58 edited 2012-01-03 00:58

  It worked! Sorta... I changed the IROut to use tx, as that's what I was actually wanting. And it, somewhat works? I also looked in the FullDuplexSerial object and I think it uses 2 stop bits, but I'm just now learning pasm, so I'm not completely sure as it doesn't say anywhere in the comments that I could find. Anyway, what it's doing now is somewhat erratic. Once again the output is below, and the first line is what I'm trying to get out, and then each group of two lines after it comes each time it transmits the byte (I added in the extra line breaks between them for clarity). A few of the lines are correct, and most are mostly correct, but have some errors in them. I'm not sure if maybe this is just due to it being done over IR/outside interference (which if so, this will definitely not work for what I'm trying) or is some timing issue or another silly thing (like attempting to send it as ASCII...)
  

  11010100 (what I'm after)
  
  10000111
  11111111
  
  00110011 (almost right)
  11111111
  
  11111011
  11111111
  
  11111111
  11111111
  
  10010110 (kinda right)
  10100011
  
  11111110
  10111011
  
  11111111
  11000011
  
  11111111
  01110111
  
  11111110
  00000011
  
  11111110
  01000011
  
  11111111
  11111101
  
  01110011
  11111110
  
  00110111
  11111110
  
  00001111
  11111110
  
  10001000
  00101011
  
  11111111
  11100001
  
  00001111
  11111111
  
  10001011
  11111111
  
  10000011
  11111111
  
  01010011 (correct! but inverted)
  11111110
  
  01010111 (so close...)
  11111110
  

  
  Thanks so much for catching that mistake, any ideas about what's causing this? lol
  
  Kenny
• MagIO2 Posts: 2,243

  2012-01-03 04:21 edited 2012-01-03 04:21

  My guess here is that the IR drivers sends 1 + 8 + 2 bits and the receiving serial driver tries to get 1 + 8 + 1. This would cause that the 2nd end-bit starts a new receive-loop which results in a lot of 1s.
  
  This explaination would perfectly match with your output. I guess that the Parallax Serial Terminal should give a description on how to start it properly.
  IRIn.start(12, 27, %0000, 2400)
  I'd expect that you can use a different setting in the %0000-parameter to switch to 2 end-bits-mode.
• MagIO2 Posts: 2,243

  2012-01-03 04:37 edited 2012-01-03 04:37

                          test    rxtxmode,#%001  wz    'wait for start bit on rx pin
                          test    rxmask,ina      wc
          if_z_eq_c       jmp     #receive
  
                          mov     rxbits,#9             'ready to receive byte
  

  this looks to me like the FullDuplexSerial expects 1+8+1 - with 1 bit to start the whole thing and then receiving additionally 9 bits. If you want to change it you have to initialize rxbits with #10 instead of #9 and then at the end of the receive-loop change this
  
  shr rxdata,#32-9 'justify and trim received byte
  
  to #32-10 as well.
  
  But as far as I remember there should be serial drivers which also allow to specify the number of stop-bits. Simple Serial maybe?
• MagIO2 Posts: 2,243

  2012-01-03 04:46 edited 2012-01-03 04:46

  PS: Just checked Simple Serial ... No ... can't set number of stop-bits there
  I don't remember where I saw that, maybe someone else remembers?
• JonnyMac Posts: 9,376

  2012-01-03 11:04 edited 2012-01-03 11:04

  Stop bits only matter on the TX side as this provides a bit of delay before the next start bit; this delay is used by the receiver to buffer what it just received. My jm_irtxserial object and FDS use 11 bits for transmitting, that is, start, 8 data, 2 stop.
  
  Simple_Serial uses one stop bit which is fine because it only supports baud rates up to 19.2K so the bit timing is quite long (relative to the time it takes to move the just-received byte into a buffer). From Simple_Serial:
  

  PUB tx(txByte) | t
  {{ Transmit a byte; blocks caller until byte transmitted. }}
  
    if txOkay
      outa[sout] := !inverted                             ' set idle state
      dira[sout]~~                                        ' make tx pin an output        
      txByte := ((txByte | $100) << 2) ^ inverted         ' add stop bit, set mode 
      t := cnt                                            ' sync
      repeat 10                                           ' start + eight data bits + stop
        waitcnt(t += bitTime)                             ' wait bit time
        outa[sout] := (txByte >>= 1) & 1                  ' output bit (true mode)  
      
      if sout == sin
        dira[sout]~                                       ' release to pull-up/pull-down
  
• Phil Pilgrim (PhiPi) Posts: 23,514

  2012-01-03 11:51 edited 2012-01-03 11:51

  You can do IR communication using FullDuplexSerial unmodified. The trick is to generate the 38 KHz carrier in the foreground using a counter, outputting to the IRED pin (see listing for correct hookup). Then FullDuplexSerial can modulate the carrier by virtue of its output to the same pin being ORed with the output from the counter. Here's the test program I used to verify the concept:
  

  CON
  
    _clkmode      = xtal1 + pll16x
    _xinfreq      = 5_000_000
  
    IR_XMT_PIN    = 0
    IR_RCV_PIN    = 7
  
  OBJ
  
    ir    : "FullDuplexSerial"
    sio   : "FullDuplexSerial"
  
  PUB  start | char
  
  '' Program to test sending serial comms via IR, using a 38 KHz IR receiver and FullDuplexSerial.
  '' The 38 KHz carrier is generated in the foreground via a counter in NCO mode on the IR_XMT_PIN.
  '' FullDuplexSerial modulates the carrier with the serial data, since a high on the pin is ORed
  '' with the the counter output. This requires the IRED to be wired for negative-going logic:
  ''
  ''      Vdd
  ''       
  ''       └───── IR_XMT_PIN
  ''        IRED
  ''
  '' The input and output waveforms look like this:
  ''
  ''                    SPACE      MARK      SPACE
  '' IR_XMT_PIN: ────┐┌┐┌┐┌┐┌┐┌┐┌────────┐┌┐┌┐┌┐┌┐┌┐┌┐┌──── 
  ''                 └┘└┘└┘└┘└┘└┘        └┘└┘└┘└┘└┘└┘└┘
  ''
  '' IR_RCV_PIN: ────┐          ┌────────┐            ┌────
  ''                 └──────────┘        └────────────┘
  
    ctra := %00100 << 26 | IR_XMT_PIN
    frqa := $001f_212d            '38000 * (1 << 32) / 80_000_000
    dira[IR_XMT_PIN]~~
    ir.start(IR_RCV_PIN, IR_XMT_PIN, 0, 2400)
    sio.start(31, 30, 0, 9600)
  
    repeat
      ir.str(string("Testing 123", 13))                   'Send string on IR_XMT_PIN.
      repeat until (char := ir.rxcheck) < 0               'Receive bytes on IR_RCV_PIN
        sio.tx(char)                                      'Echo received bytes to PC.
  

  
  -Phil