Most customers using our stepper motor controllers have no problems when they operate them with the Parallax Basic Stamp or Javelin Stamp products.  However, a few have had some issues; this note summarizes the steps which you should go through, if your first attempt does not appear to work.

Before you connect the Parallax Basic Stamp (or Javelin Stamp) to our products, you should first test our board in a stand-alone configuration and with Hyperterminal to make certain that you have the motor correctly connected to our controller. 

As an absolute stand-alone test, refer to our manual section "Stepping sequence, testing your connection".  In that section, we describe shorting one of our "slew y" input pins to ground, in order to cause the motor to spin (as a test for whether you have the correct order of wiring in the motor).

The next test is to use the windows application "Hyperterminal" to test the unit (with the controller still disconnected  from the stamp and the serial buffer re-enabled (add the JS jumper back or re-insert the Max232 chip)).  Please review our page "Using Windows Hyperterminal" for more information on setting up Hyperterminal for testing the product.  If Hyperterminal will not "talk" to our board, then something is wrong, and the stamp will probably not successfully control our board either.

When you connect the Parallax Basic Stamp series of controllers to any of our stepper controller boards, there are several items which you must be careful to do:

1. Make certain that both the Stamp and our board's logic are run off of the same power supply.  If this is not possible, make certain that the "GND" line of the stepper controller is connected to a GND on the Parallax board.
2. When you actually try to run your Stamp application, disconnect the "download" programming RS232 cable from between the computer and the stamp.
3. Remove the "JS" jumper from our board (Jumper Serial), if you have the BiStepA06, BiStep2A05 or SS0705 unit.  If you have the BiStepA04, BiStepA05, BiStep2A04 or SimStepA04, remove (and save) the Max232 serial controller chip which is located right by the 9 pin serial connector.
4. Make certain that you have adjusted our sample code to match your stamp product.  Different stamps require different settings for the "PortStepperBaud" parameter used in our samples.
5. Use a linear power supply, not a switching power supply.
6. Make sure your power supply is large enough to meet the demands of your application.
7. Keep your leads between the two units short .   TTL signals are only "clean" (that is to say, little "bounce" or induced voltages) at up to 3 feet.   
8. We suggest always running communications at 9600 baud. 

Discussion:

1.  Using a common power supply for the boards avoids ground referencing problems.  This is the single most common cause of issues when using the stamp.  If separate supplies must be used, then you must be certain that you connect their grounds together with a reasonable size wire, in order to make certain that both boards "float" at the same potential.  Otherwise, TTL signals will not be correctly interpreted, and serial communications will fail.

2.  We have often had issues with ground-distortion induced by leaving the serial cable (used to program the stamp) connected while trying to have the stamp "talk" to a stepper controller board.  Merely unplugging the cable has always been enough to "fix" the problem.

3.  Removal of the JS jumper or the Max232 chip is needed to avoid connecting the outputs of two chips to each other.  Leaving the JS jumper (or Max232 chip) installed results in  what is called a "wired or"; and can cause eventual failure of the chips involved.

4.  When you edit the sample code for your system, you need to look for the line which contains the "{$STAMP" command, and adjust it to match your stamp (such as BS2, BS2sx, etc.).  You then need to edit the line which defines the "PortStepperBaud" parameter to contain the correct value for your stamp.  Please refer to your stamp manual for the values.  For some of the stamps, the values are:

For example, to generate 9600 baud on a BS2sx, you need to have the PortStepperBaud line contain:

    PortStepperBaud con 240 ' Baud rate to generate 9600 baud on BS2sx

5.  Use of a linear power supply (as opposed to a switching power supply) is a very strong recommendation.  Switchers generally do not have the short-term power reserves needed to handle the extreme variances in power which are demanded on motor startups, and they are usually much "noisier" from an electrical point of view.  We have had no reported power-supply related problems when our customers use linear supplies; we have had frequent issues when switchers are used.  For example, switchers will often have 10-20% of "ripple in their voltage (i.e., there will be a periodic variance of several volts in their supplied power, usually at the line frequency of 50 or 60 hz).  This means that the motors are "feeling" a 10-20% variance in their drive power, which means that microstepping will be unreliable in position.

6.  We have frequently had customers complain that their motor stalls or does not appear to have enough power.  In most cases, this has been traced to the customer having selected a power supply which can only deliver about 1/2 of the current required by the motor!  Remember that a stepper motor can have 2 windings on at a given time -- this means that it can draw twice as much current as you would expect, if you just look at the current rating of the motor.  Please refer to our web page, Calculating Motor Currents, for a rather complete summary of how to calculate the current requirements for your application.

7.  TTL signals are quite susceptible to induced voltages from antenna effects, impedance matching issues, and from neighboring signals.  In general, when the signals are kept to under 3 feet, the amount of induced signals are too small to cause a logic circuit to trigger.  When operating using TTL-Serial mode (as opposed to RS232 serial, which uses much larger voltages) on a 26 foot cable, we have found that there can be about a 0.1 microsecond wide 5 volt spike induced onto one signal line when a neighboring signal line changes state (i.e., when a serial bit is sent to our board, a narrow spike can be induced on the serial output line from our board to your stamp).  Due to the nature of the serial timing between the products, this spike is normally ignored under serial I/O (our firmware rejects it via a digital filter, and the timing of serial I/O to and from the stamp is such that the stamp would not see it).  Our suggestion of 3 feet or less avoids this potential issue.

8.  The most recent versions of the firmware (for example, GenStepper version 1.75) has enough idle time built into it when operating in the suggested modes for Stamp communications that you should have no problems.  Operate at 2400 baud only if you cannot get reliable operation at 9600 baud (and even then, you should contact us for further suggestions!).

Some Explicit Stamp Connection Examples

This section contains several examples of connecting Parallax Stamp-based products to our stepper controller boards. 

In each case, the connections shown are a combination of those required to use the sample programs which we provide with the stepper controller boards.  This means that the following signals are connected:

The following photo shows a complete setup of a Parallax “Board Of Education”, wired to a BiStepA06 board.

A “zoomed in” image shows the signals a little bit more clearly:

Observe that the ground between the boards is accomplished by a wire from the extra “GND” connector on the BiStepA06 power connector (lower right of board as shown) to one of the “Vss” signals on the BOE.

Also observe that the P1àSO, P2àSI, and P3àRDY signals actually go “straight across”: the signals line up in a set of rows.

An identical setup using the NX-1000 board looks as follows:

Similarly, a “zoomed in” image just showing the key signals appears to the left.

In this case, the extra “GND” signal on the BiStepA06 is run to the “GND” connector which is beside the P0-P15 signals on the NX-1000 board.  As with the BOE, the P1àSO, P2àSI, and P3àRDY signals are all consecutively aligned, and operate without any signal wire crossings.

 In both of the above examples, power was supplied by switching power supplies in the form of  “power bricks”.  While we strongly urge that such items not be used, they can work if they are wired as described in the above lists.  A photo of the supplies correctly plugged into a grounded power strip follows.  Please observe that they are both plugged in “facing” the same way, so that the neutral wire is on the same side for  both plugs.

Finally, if you have any problems which the above set of actions do not appear to be able to resolve, please do not hesitate to contact us at our customer support email address (support@stepperboard.com) or via the telephone.  Our phone numbers for contact are:

U.S. Toll Free:  877-230-5270

International: 314-521-8808