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How to check for DEAD PROP/EEPROM/XTAL? — Parallax Forums

How to check for DEAD PROP/EEPROM/XTAL?

DavidMDavidM Posts: 630
edited 2008-01-06 21:56 in Propeller 1
Hi,

I have just soldered up a new PCB ( my own design) which uses the PROP ( DIP40 ) an eprom and xtal. I "SALVAGED" these parts from another board I made some time ago, which I think could be suspect?

I had to de-solder the xtal and reuse this on my new board, The Eprom & PROP are in sockets but were used before.

I hooked up my prop plug and pressed F7 in SPIN and the SPIN APP cannot detect a propeller device!

I am getting all the correct voltages where they are required on the parts and other places on my PCB, ( i.e 3.3 v GND etc)
My circuit ( And soldering) seems to be correct as far as I can see.

I don't have any spare parts to do a swap! So ...

Q1) How do I test which part is faulty? The PROP the EEPROM or the XTAL?? I only have a basic multi-meter

Regards

Dave M

Comments

  • deSilvadeSilva Posts: 2,967
    edited 2008-01-06 01:01
    As things are in sockets this is extremely easy
    - Take a solderless breadboard
    - Insert Prop and EEPROM
    - Insert a four header pin
    - connect them all with 12 wires and one 10k resistor
    - connect a 3v3 power supply (or get it from a 5V supply, adding a IR diode)
    - connect the Plug and try
    F7
    F10
    F11

    P.S.: Everyone should get started that way in the first place... Boards... Good heavens!

    Post Edited (deSilva) : 1/6/2008 1:08:04 AM GMT
  • Mike GreenMike Green Posts: 23,101
    edited 2008-01-06 01:06
    The identify function of the Prop Tool does not require a working EEPROM or a working crystal. Only the Prop itself and the serial port (with DTR triggering a reset) have to work. During the reset function / boot loader, the Prop runs off its internal fast RC clock and you can download and run programs without an EEPROM attached. Check all the Prop connections and the serial port.
  • DavidMDavidM Posts: 630
    edited 2008-01-06 01:31
    Thanks DeSilva & Mike!

    So I only need to test the PROP itself, This narrows it down! smile.gif

    I will try the above suggestions?


    Regards

    Dave M
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-06 01:37
    You should START with just checking the Prop alone!
    If it works add the EEPROM

    There can be no problem with the crystal as it is not used for F7
    However you might run into problems when your OWN CODE runs using the crystal if it is defective...
  • DavidMDavidM Posts: 630
    edited 2008-01-06 02:38
    HI,

    I made up a breadboard with the basic PROP ONLY circuit, Pressed F7 and it Still did not work!

    This is good & bad news!

    Bad news . I damaged my prop! :-(

    Good news , My PCB design might still be OK! smile.gif


    Thanks Guys for your help,

    Time to buy some props!

    Regards

    Dave M
  • hippyhippy Posts: 1,981
    edited 2008-01-06 03:24
    DavidM said...
    Bad news . I damaged my prop! :-(

    Good news , My PCB design might still be OK! smile.gif

    Or maybe vice-versa. Particularly check that you haven't crossed over TX and RX between the programming interface and the Propeller Chip.

    You could try the Propeller chip in a beadboard with just the minimal connections and see if it works there.
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-06 03:31
    hippy said...
    You could try the Propeller chip in a breadboard with just the minimal connections and see if it works there.
    This was my plan...
  • DavidMDavidM Posts: 630
    edited 2008-01-06 05:08
    HI Guys,

    I made sure that the RX & TX were correct!

    The TX from the prop plug goes to the RX (P31) of the prop , and ..
    the RX from the PLUG goes to the TX on the PROP (P30)

    One other question..

    There are 2 VDD & VSS pins on the prop, I tested it with both pins hooked up accordingly,
    but can you use just 1 of Each? That is the VDD & VSS next to the BOEN & RESN pins?

    Thanks

    Dave M
  • LeonLeon Posts: 7,620
    edited 2008-01-06 06:51
    You should use both supply pins, they are needed to distribute the power properly across the chip.

    They should be decoupled, as well.

    Leon

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  • DavidMDavidM Posts: 630
    edited 2008-01-06 06:53
    Thanks Leon,

    I Have them both used in my PCB design and I have a de-coupling cap across them. For the text I used both as well but I did not place a cap.

    Thanks

    Dave M
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-06 13:52
    David,
    when you get a new Propeller, just test it first in your new "test rig". It should work there...

    Other tricks:
    * You can connect the Propplug in such a way that rx/tx directly fit into the last two Propeller pins. Next to the outside comes Reset -> wire to reset pin

    * Breadboards have those cut in the middle of the rails, one sometimes forgets to bridge it
    * As Leon already said: It is indespensibla co connect both sides of the power supply; there can be strange effects if you do not.
  • DavidMDavidM Posts: 630
    edited 2008-01-06 21:56
    Thanks deSilva!

    Dave M
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