Reading smart motor data with db9 through max232

Comments

• Duane Degn Posts: 10,588

  2016-09-06 20:36

  mechqueen wrote: »

  I also have the TX going to P4 and Rx Going to P5 on this board because my usb from my computer
  is inserted into the board, so that takes care of my onboard tx rx going directly to the Q44 chip.

  
  I haven't looked at the code yet but I wanted to warn you about using 5V logic signals with the Propeller. You need at least a 3.3K resistor in series on the rx line from the MAX232 chip.
  
  I'll take a look at the code a bit later if no one else beats me to it.
  
  
• mechqueen Posts: 3

  2016-09-06 20:41

  Yes, thank you. I already do have a resistor in series with the rx line which is bringing my voltage down to 3.30.
• Duane Degn Posts: 10,588

  2016-09-07 00:17 edited 2016-09-07 18:54

  I haven't tested this but it should let you see any non-printable characters.
  

  CON
  
    _clkmode = xtal1+pll16x
    _clkfreq = 80_000_000
  
   
  
  CON
                                    'Note Clock Speed for your setup!!
  
      COM11_RX = 4
      COM11_TX = 5
  
      COM12_RX = 31
      COM12_TX = 30
  
      BAUD_RATE = 9600
      
  
      
  OBJ
    uart1     : "FullDuplexSerial"
    uart2     : "FullDuplexSerial"
  
  PUB Main
  
  
    uart2.start(COM11_RX, COM11_TX, 0, BAUD_RATE)
    uart1.start(COM12_RX, COM12_TX, 0, BAUD_RATE)
  
    repeat
      result := uart2.rxCheck
      uart2.str(string(11, 13, "Press Any Key"))
      waitcnt(clkfreq / 2 + cnt)
    while result == -1  
  
    uart2.tx(16)  ' clear screen
    uart2.tx(1)   ' home
    uart2.str(string(11, 13, "Data Logger v.1"))
    uart2.tx(11) ' clear end of line
    uart2.tx(13)
  
    'echo everything out
    repeat
      result := uart1.rx
      SafeTx(result)
       
  
  PUB SafeTx(character)
  
    case character
      13:
        FramedHex(character)
        uart2.tx(character)
      33..126:
        uart2.tx(character)
      other:
        FramedHex(character)
  
  PUB FramedHex(character)
  
    uart2.tx("<")
    uart2.tx("$") 
    uart2.hex(character, 2)
    uart2.tx(">")
  
• mechqueen Posts: 3

  2016-09-07 17:34

  Oh wow. Thank you. I will see how this works and post back.
  
• Duane Degn Posts: 10,588

  2016-09-07 18:51

  I just noticed a mistake. That's what I get for not testing it. I'll fix in a few minutes.
• Duane Degn Posts: 10,588

  2016-09-07 18:55

  I fixed the embedded code above and I've attached the corrected Spin file to this post.
  
  I still haven't tested the code but this version has a better chance of working.

  spin

  spin

  serialBridge160907a.spin

  1K

  serialBridge160907a.spin 1.1K
• Cluso99 Posts: 18,069

  2016-09-13 06:21

  I have the gnd and 5v of out of the max232 coming into the board with the Q44 Propeller Parallax chip on it
  going to V5 and Gnd.

  
  I do hope you are using 3V3 on the propeller chip???
  
  I see the schematic shows all 4 sets of power and ground are connected and with bypass capacitors. I presume you have a propplug to program your propeller (It appeared to be a separate connector on the schematic. If you build your own propplug you will need the transistor reset circuit. I like a 10K pullup on the prop RST pin as it helps to prevent noise causing an unwanted reset.
• kicadguru Posts: 1

  2021-08-08 16:33

  Is there any difference between using a modern MAX232 variants vs the older ones. The new ones all point to a datasheet that is over 20 years old! see attached PDF file. I'm guessing it's just to conform to RoHS.

  pdf

  pdf

  max232.pdf

  358K

  max232.pdf 358.4K
• Circuitsoft Posts: 1,166

  2021-08-20 10:35

  You probably should use a max3232, which is made for 3.3v instead of 5v.