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Successful communication using the 3-Transistor adapter! — Parallax Forums

Successful communication using the 3-Transistor adapter!

Brandon C.Brandon C. Posts: 106
edited 2009-06-22 05:05 in Propeller 1
Hello everyone,

I was not able to get my 2-transistor serial adapter to work with the propeller, but I headed over to radioshack and picked up a 2N3904 transistor and made the 3 transistor version. It works perfectly! on the first try after 15 minutes of building the circuit, I had a working propeller. I am so happy! tongue.gif

I uploaded a video of the blinking LED program running on the chip.

www.youtube.com/watch?v=x5OZ2iO_PFo

here's a pic:


adapter.png


Brandon C.

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No purchase necessary. See back panel for more details.

Comments

  • KyeKye Posts: 2,200
    edited 2009-06-19 03:52
    Good for you.

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    Nyamekye,
  • Oldbitcollector (Jeff)Oldbitcollector (Jeff) Posts: 8,091
    edited 2009-06-19 03:57
    Awesome!

    Wish someone would do blank PCB's for that circuit.
    Would be a nice option for budget propellerheads.

    OBC

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    New to the Propeller?

    Visit the: The Propeller Pages @ Warranty Void.
  • Bill HenningBill Henning Posts: 6,445
    edited 2009-06-19 05:01
    I have done a PCB layout, however the 3 transistor circuit did not work on 3 out of 3 USB->serial cables I tried. It did work with the built-in comm port of the PC.

    I can make and sell the boards, but I cannot guarantee they will work.
    Oldbitcollector said...
    Awesome!

    Wish someone would do blank PCB's for that circuit.
    Would be a nice option for budget propellerheads.

    OBC
    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Las - Large model assembler for the Propeller (alpha version released)
    Largos - a feature full nano operating system for the Propeller
    www.mikronauts.com - a new blog about microcontrollers
  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-06-19 08:57
    Elektor did a small card to minic the USB programmer,·on a Boe Bot prop thing a couple of years back. It was a 9 pin D type to 0.1" sockets, it did·need a fifth pin for +3.3V as there is no power from the USB cable. I'll see if I can find it later.

    USB to RS232 converters just can not be relied upon to give correct handshakes, and so give DTR for the reset.

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    Style and grace : Nil point
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2009-06-19 09:29
    @Brandon

    That's really cool!
    If it could be made to work reliably even with the USB to rs232 adapter it would be a great circuit to
    add to a project board smile.gif

    I could sure use a good circuit like this...I just know I'm going to lose every proplug thing we buy, they are sooo tiny!
    (I'm thinking of using epoxy glue to affix a USB cable permanently so I don't lose them)
  • StefanL38StefanL38 Posts: 2,292
    edited 2009-06-19 12:18
    My experience with USB-RS232-adapters is

    adapters with a prolific-chip do NOT work reliably with the propeller

    FTDI-chips DO work reliable with the propeller

    best regards

    Stefan
  • Brandon C.Brandon C. Posts: 106
    edited 2009-06-19 13:02
    Thank you all for the comments!

    @OldBitCollector
    I would make some blank PCB's and sell them but as others have said they aren't very reliable. I would not like for someone to be disappointed if the circuit did not work.

    Brandon C.

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    No purchase necessary. See back panel for more details.

  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2009-06-19 13:27
    Rather than using transistors I use a common logic gate (74HCT132) to handle the inversion etc. But rather than bothering to generate a redundant negative voltage my circuit swings from rail-to-rail. Does it work? Of course it does, never fails, whether it is connected directly to fixed serial ports or USB to RS-232 adaptors. The Prop side is identical to the Proplink except I also have another row of pins that include VDD. Another advantage of using logic gates is that it can operate at higher speeds than a passively loaded transistor driver. After all the transistor circuit is implementing a primitive logic inverter.

    Talking about pcbs, here it is. I made these up as I got sick of throwing transistors together. Even though they are smd they are very easy to assemble as you only need a normal soldering iron.

    *Peter*
    PL1-232.png
    619 x 314 - 11K
  • mikedivmikediv Posts: 825
    edited 2009-06-19 22:52
    Good job I still get excited when I build something and it works properly ,, Gee whats wrong with us

    Peter Jakacki darn that's small can you solder that yourself ???? is it all SMT??? very nice by the way I have a pretty nice iron a few of them actually and mine always gets glazed over when I am using them thenb the solder will not melt and I end up getting a big glop
    and its a mess even if I wipe the iron a lot when using it I can not imagine doing SMT , do you use a low heat iron?? mine is variable but I crank it to 480

    Post Edited (mikediv) : 6/19/2009 10:58:16 PM GMT
  • VaatiVaati Posts: 712
    edited 2009-06-20 00:09
    Oh

    My

    Gosh


    I have pondered over my three transistor circuit for sooo long now...




    I feel like hiding in a corner and trying to fix my SD card adapter...

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    Quit buying all those fixed voltage regulators, and·get an Adjustable Power Supply·for your projects!· Includes an LED testing terminal!
  • Brandon C.Brandon C. Posts: 106
    edited 2009-06-20 17:55
    Keep trying! the only thing that kept me going is that I was too excited to wait a month to buy a PropPlug! turn.gif


    Brandon C.

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    No purchase necessary. See back panel for more details.

  • Toby SeckshundToby Seckshund Posts: 2,027
    edited 2009-06-20 21:42
    Holly summed it up, prop-plug ... Absolutely fantastic (now where is that little b******). I build things out of gutted things so the latest cutting edge stuff is just a, cute, pipe dream. But when the one thing you wanted gets to work, and has been struggled so much for, it's one billion times better than the latest evaluation offerings, that does more but only that which they gave you. And it doesn't matter if it had one transistor or twenty core procs.

    Right now back to using a PC and a CPLD to emulate some TTL, Hey-Ho.

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    Style and grace : Nil point
  • Beau SchwabeBeau Schwabe Posts: 6,572
    edited 2009-06-21 07:09
    @Brandon C.

    Everyone should know, that the only reason the 3-transistor circuit exists is because I managed to come back from California without my PropPlug and I was desperate to get things going. No, it's not a perfect circuit, and I borrowed much of the design from a tried and true circuit that is currently used in the BS2 modules. The reason that some USB to RS-232 adaptors don't function is because the 3-transistor circuit really "expects" RS232 levels and the USB to RS-232 adapters generally don't provide that. Now, you might get lucky on the 3-transistor circuit and choose your transistors that happen to have a really high Hfe and it will work at the lower level voltages, but the 3-transistor circuit is really looking to be plugged into a PC "with" a real COM port. Additionally some USB to RS-232 adapters do not properly bring out the DTR line which can cause the IDE to not recognize the Propeller properly.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • nightwingnightwing Posts: 56
    edited 2009-06-22 05:05
    Interesting circuits... Need to try the IC one... New one on me...

    Have the two transistor working. Found it in a parallax manual. Looked good so built it and it work. Connector is a bit loose but works with std RS232 and a cheep USB to RS232 ( Prolific USB-to-Serial Bridge ). Was in a hurry so used two .05 instead of a .1 as the original circuit called for.

    If you don't mind what is the diagram for three? Be interesting to try it...

    Here is the one I cooked up... With USB adapter connected... Click on pix for bigger versions...

    Top View: 570449034_8kWrc-Ti.jpg Bottom View: 570448655_LdPM6-Ti.jpg
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