serial connection-disconnection problem with propeller 1

Hi Guys,
I use already some years propellers for different projects. Now I used a propeller that collects data and store these in an area of bytes.
To see the results of he collected data I connect a PC to the serial port and this works fine. Until I disconnect the PC and want to reconnect it. The propeller goes to reset and I loose the program and the collected data. The program is written in SPIN and works fine until you disconnect the PC. This does not happen every time but at least after 3 or for times. I than putted the program in EEPROM and again, when I disconnect the PC and reconnect it, the program resets.
Does anyone have the same problem?
I tried the same exercise with only a serial connection without the use of a serial/usb plug but the results are the same.


  • msrobotsmsrobots Posts: 3,275
    edited 2019-09-27 - 18:55:40
    A couple of things come to my mind here, but all are related to the use of USB. The problem seems to be that outputting data to the USB chip when it is not connected to a PC will power it up and it does reset the P1.

    Same goes for connecting/disconnecting since the PC will enumerate the USB devices and reset the P1 also.

    Sadly Parallax does not sell boards without USB anymore so the only way I know around this is to physically modify the used board, cut the connection to the reset of the P1 and replace it with a jumper for programming and jumper off for running.

  • Thanks Mike for your fast response. I did disconnect the rst from the P1 but this did not solve the problem.
  • hm.

    How do you power the board and what board is it exactly?

    I still have some protoboards w/o USB and those guys are running for weeks.

    Have you tried different pins and a PropPlug?

    there should be some reason.

    can you maybe post the code?

  • I tested it with a Propeller Activity board Rev A using a power supply of 7,5V-1A. The actual design I am testing is a self developed board using a 40 pin
    P1 and a powersupply design to overcome outlet power failure. I attached the design in ODG extension since I only use Linux as an OS. The program, also attached, works OK and as long as I do not reconnect the PC to read the data using the '120' value inputted to the terminal.
  • Your rectifier for 220VAC is facing the wrong way.
  • Sorry for the drawing error Frida.
    The rectifier is rightly connected on the board. The idea of the project is to detect any power interruption at a connected input. The inputs are selected with the rotary switch and can be the outlet voltage(220VAC), 12 or 24VDC.
    Thanks for your remark end I will correct the drawing.
  • Hi Guys
    Problem of the program loss is solved in two steps;
    - disconnecting the 'reset' during normal communication with a switch interrupting the 'RES'line
    - putting a 6.8µF near to the P1 power connection.
    Thanks for the info which putted me to look further.
  • drawing of the adapted system
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