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Basic Stamp 2 can not be identified — Parallax Forums

Basic Stamp 2 can not be identified

ECSimsECSims Posts: 19
edited 2008-02-01 21:54 in BASIC Stamp
I had this strange thing happen yesterday.··I plugged in a board that I built using the Basic Stamp OEM Lite schematic that Chris·posted, and it worked for·about 10 seconds, then it·quit all together.····I built three other boards like this, and they all worked flawlessly.· The prop plug is communicating with the software, but it can not idenify any device.· I am receiving an echo on COM8, but it can not find a device type.· When I try to compile, it says "No Basic stamp found".· I checked for power on the BS2, and it showed 5Volts.· What else should I be checking?· How do I diagnose this problem?

Help would be greatly appreciated!!!!

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-28 20:51
    "Echo" and "Loopback" are almost entirely hardware related. They validate that your cable is plugged in (Loopback) and that the RS-232 voltage conversion transistors are working ("echo").

    Anything more requires a working, correctly powered BS2. Low batteries can cause this, as can missing/bad ground connections.

    You sure the chip isn't in upside down?
  • ECSimsECSims Posts: 19
    edited 2008-01-28 20:57
    Yes, I am sure it is not upside down. I will check carefully the ground connections to the chip. Any other suggestions? Thanks!!
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-28 21:20
    Once upon a time, Sams published very nice Television troubleshooting diagrams, which included what your Oscilloscope should see at various test points in the signal flow. Sadly, I haven't seen such a thing for the OEM BS2. I'd expect to see some cycling on the line to the external eeprom, at least.
  • ECSimsECSims Posts: 19
    edited 2008-01-28 22:30
    I am comparing a good board with a bad board and these are the voltages I am reading when I probe the BASICSTAMP2 chip with the power on the board.



    ···························· "Good" Board·· "Bad" Board

    Pin #· Pin name·······

    1········RTCC················ 0V················· 0V
    2······· Vdd·················· 4.9V··············· 4.9V
    3······· NC····················na·················· na
    4······· Vss·················· 0···················· 0
    5······· NC··················· na··················· na
    6······· RA0·················· 2.7V··············· 266mV
    7······· RA1·················· 1.2V··············· 1.4V
    8······· RA2·················· 3V·················· 2.7V
    9······· RA3··················· 4.9V···············2.4V
    Pins 6-7 Go to the EPROM
    Pins 8-9 go to the Prop Plug

    10-25· These go to my buttons and knobs
    26····· OSC2·················2.2V··············· 2.2V
    27······OSC1················ 2.2V················2.2V
    28····· MCLR················ 4.9V················ 0.6V

    Based on this data, I suspect pins 6 (connects to DATA on the EPROM), pin 9 (connects to the diode, then to the Prop-Plug), and pin 28 (connects to MCLR.··· The OEM sematic is posted here:· It is in the completed projects forum.

    http://forums.parallax.com/showthread.php?p=567989

    I am at a loss about what do check for next.· Thanks!
    ·
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-28 22:38
    Um -- I'm pretty sure MCLR is an 'active low' signal -- so something pulling it down to 0.6 volts will hold your BS2 OEM in 'reset'. You might trace that signal -- it SHOULD come from the DTR line of your PC (eventually).
  • ECSimsECSims Posts: 19
    edited 2008-01-28 23:14
    Yes, I will check that one out. You don't suspect pin 6... or 9 for that matter? Thanks a million!!
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-29 03:57
    If it's being held in 'RESET', then I assume they're being held in "input" mode (high impedance). Fix the 'RESET' signal first, then you can look at RA0..3.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-01-29 17:08
    The /RESET line may be a result of the brownout detector being improperly installed.

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    Chris Savage
    Parallax Tech Support
  • ECSimsECSims Posts: 19
    edited 2008-01-29 17:53
    Hi Chris,

    I left out the brown-out detector.· It was not included.· I could not find anything wrong with the wiring.· I am still at a loss. I may just throw out the board and start from scratch.

    I mounted the prop-plug directly on top of the PCB board.· I had to remove the plastic Prop-Plug label in order to get it to sit flush and low profile.··· I am thinking I may have caused a short on the Prop-Plug by mounting it directly on the board.· I will place some insulation under the Prop-Plug and see how that works out.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-01-29 20:23
    Well if any traces from the two circuits are touching that could be it. One line from the Prop Plug connects to the /MCLR (/RESET) line so your problem could be there as well. The output from the Prop Plug is essentially an NPN transistor and would be there. I highly doubt it could be the FTDI Chip since a capacitor prevents that output from being held in that state.

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    Chris Savage
    Parallax Tech Support
  • ECSimsECSims Posts: 19
    edited 2008-02-01 04:40
    I solved my problem with the Basic Stamp not identifying.· Strangely enough, it had nothing to do with the PCB board, and the connections that I made.

    It seems as if the order in which you power up the board, plug in the USB, and compile the code is very important.· It has to be done in this order:

    1) Open the Basic Stamp software
    2) Power up the PCB board
    3) Plug in the USB cable
    4) Press Play to upload your code to the Stamp

    If the debug screen is all ready open when you plug in the USB, the Stamp will not be identified.
    If your board is not powered up when you first plug in the USB, then the Stamp will not be identified.
    .
    This quirky behavior occurs for both the Prop Plug and the USB2SER.

    Can anyone explain why it is so finicky?· I was racking my brains trying to figure out what was wrong for days!

    Eric
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-02-01 14:51
    Welcome to the USB "identify" cycle.

    USB is a very nice, and very flexible standard. However, you DO have to have a USB 'master' (your PC) and a USB 'slave' (your board).

    USB was designed to be 'hot pluggable'. When you first plug in a USB device, there's an "identify" cycle the USB hardware/software goes through. This lets the "master" load the correct driver code into the 'master' for the 'slave' hardware, so the "master" can communicate properly with the 'slave'.

    The result of all of this is that the USB "Serial Port" that your BS2 board uses doesn't "exist" at all on your PC, until AFTER you plug in your fully powered USB connection. So, if you bring up the IDE and Debug screen first, it doesn't find that "serial port", and doesn't know to use it.

    I would assume you could plug in the fully powered USB connection BEFORE you brought up the IDE, though.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-02-01 21:54
    When the USB circuit is powered from the PC as it is on our boards, the COM Port should identify, unless, as you said, the DEBUG is opened, which means it has a hold on the port. As a side note that issue has been correct in the current version (V2.4) of the BASIC Stamp Editor.

    If the BASIC Stamp starts sending data (using DEBUG or SEROUT) through the port before the USB cable is connected, the PC may see the device as a mouse. This is why we recommend having our development boards powered off when connecting the USB cable. When it is detected as a mouse the BASIC Stamp Editor cannot see it, and in some cases it can affect your normal mouse movement.

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    Chris Savage
    Parallax Tech Support
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