Quadcrawler servos testing. How ?

inakiinaki Posts: 262
edited 2005-02-06 - 05:23:31 in Robotics
I have problems testing the servos on the quadcrawler. The test programs I have used to check the PSC controller board do not work at all. In other words, I cannot see the PSC board from the BS2.

If I understanad well the serial port is connected to PIN 15 on the BS2·at 2400, no parity, 1 bit stop. The servo controller does not have the usual auto-sense feature. I have used this configuration on the code.·However I cannot·connect to the·PSC from the BS2. I have tried using the test·program listed in the PSC manual.·This program sends the comand "!SCVER?" and tries to get back the version of the board, for example: 1,2,3.· However I cannot get back any meaningful number. As expected, the more ellaborated programs that come in the same manual, and the simple test program that comes in the Quadcrawler Kit manual·do not work.

I am afraid something is failing on the serial communication or even on the PSC board itself.If with the BOE disconnected from the PSC·I turn the switch·ON on the PSC board·some motors move a bit, others move a lot and·finally others do not·move at all. I have used other servo controllers but this one does not seem to send any pulse by itself (for example, other controllers try to center the motors at start time but this one does not do much).·The two leds on the center of the PSC·board work as follows: the one on the bottom of the chip is ON all the time; the one in the top blinks for some time, then stops and gets OFF.

To power the boards I use a 9V battery for the BOE and a 7,2V pack for the servos.·The servo power selector on the BOE is set to Vdd.

Regarding the serial cable that connects BOE and PSC,·the pictures on the manuals suggest to use the first slot X4 slot on the BOE·and the serial in slot on the PSC. So I am pretty positive I am connecting this cable the right way. Apparently this cable connects the PIN15 and Vss from the BOE to the PSC.

I have checked that wires coming from the servos are properly atached to the PSC. Actually if the servo cables are twisted the leds do not light up.

Supposing I am connecting all right what do you think I might be doing wrong to get no answer from the servos ?



  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-02-06 - 05:23:31
    In your post you mentioned the power to the BOE, and the power to the servos, but you didn't specify power for the logic on the PSC...

    Normally you would have a 3-pin cable from the X4 jack on the BOE to the PSC, this would supply power, ground and signal.· If however you simply brought pin 15 to the PSC, you may be missing power and/or common ground.


    Post Edited (Chris Savage) : 2/6/2005 5:26:49 AM GMT
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