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USB Adaptor Board FT232RL - Self Powered & RESET Resistant — Parallax Forums

USB Adaptor Board FT232RL - Self Powered & RESET Resistant

DavidMDavidM Posts: 630
edited 2010-03-03 05:53 in Propeller 1
HI,

I have posted before, My USB Adaptor board for the Propeller which has a RESET DISABLE Circuit to overcome the rest issues with the Prop chip ( this works very well), I have now changed it to be self powered by 3.3V from the PROP Side. Instead of the USB Bus side.

Q1) Do I still need the 2 resistors for the RX & TX Lines?

Q2) I have removed the INDUCTOR from the 5V USB Input, Is this needed for Self Powered?

Q3) The FTDI Datasheet specifies 3 Capacitors (100NF X 2 & 4UF7 ) for input filtering on the VDD, I have made it so, Is this really required?

Q4) This circuit now has a connection from the 5V USB side to the USB RESET, I gather this is for keeping the USB chip "Alive" whilst plugged in, But I also think this will case the FD232RL chip to reset/restart and this may toggle the DTR line, But my RESET DISABLE circuit should handle this. So would this be a new problem?


Thanks

Dave M
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Comments

  • BradCBradC Posts: 2,601
    edited 2010-03-01 14:31
    DavidM said...
    I have now changed it to be self powered by 3.3V from the PROP Side. Instead of the USB Bus side.

    I'm interested in the logic behind that decision. Can you elaborate a little?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    You only ever need two tools in life. If it moves and it shouldn't use Duct Tape. If it does not move and it should use WD40.
  • ke4pjwke4pjw Posts: 1,173
    edited 2010-03-01 17:09
    I think he is speaking of when you have the USB converter attached and the prop transmits data (such as debug info) while the USB converter is disconnected from your computer, it will cause the prop to reset it self over and over again.

    I had one hell of a time yesterday attempting to figure out what was causing mine to do that. If the USB converter was powered from the protoboard side, it wouldn't reset.

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  • DavidMDavidM Posts: 630
    edited 2010-03-01 23:18
    Hi BradC & ke4pjw,

    thanks for the replies,

    in a previous post by me..
    http://forums.parallax.com/showthread.php?p=879140



    My USB Chip was normally powered by the USB BUS, After modifying my board ( with a diode for the power) to run from the "PROP" side i.e ( SELF POWERED) my resetting issues were solved!
    the diode was just a temporary fix of the current pcb design. I was also getting the LEDS flasshing about every 10 seconds or so, there was some kind of polling going on on the USB chip? This was fixed as well.

    The design I posted in THIS thread is my FINAL? design with those mods and after more reviews of the FTDI Datasheet this is what I have come up with.

    I am hoping to make the MOST PERFECT USB ADAPTOR for the prop!) wink.gif

    *)My reset disable circuit works perfectly, this allows plugging and unplugging of USB cable whilst powered up without resetting
    *)Opening and closing of PORTS on the PC or MAC without resetting the PROP device.
    *)Prevent any FIRMWARE UPDATING of the prop ( unless the reset disable is ENABLED on the prop side)


    thanks

    Dave M[noparse][[/noparse]url]
  • DavidMDavidM Posts: 630
    edited 2010-03-03 05:53
    HI BradC


    Did you check out my previous posts regarding this USB/Serial Adaptor

    regards

    Dave M
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