[speedydumpster]

To whom it may concern:
I have about 7 or 8 VSD-E drives, and currently I have one 3x mill that I am using 3 drives in and controlling them in torque mode with the analog in. I would like to switch the communication to use SPI rather than the analog input, as when I first start up the mill the slight voltage on the analog input causes the axis to take off, and can potentially cause a crash. It is quite unnerving.

So I would like to switch the communication directly to SPI. Do you have any documentation on how to control these drives directly using SPI. I looked up the documentation on your SimpleMotion utility, but what do you use to communicate to the drive directly through SPI? Are there any special commands?

Here is the controller that I am using. Please let me know this is possible to do.
RS232 with KFLop
Thank you,
Dave

[TomKerekes]

Hi Dave,

The normal way to solve the drift problem is by using the amplifier enables. On power up the amplifiers should remain disabled until the system is initialized and the servos are enabled. Once the servos are enabled they will hold position without any drift.

Your link is to our RS232 UART not a SPI port. KFLOP doesn't have a hardware SPI port. But there was a discussion on the Yahoo Group on how to bit-bang an SPI transfer in software. It runs at about 500Kbits/sec.

HTH
Regards

[speedydumpster]

As always, thank you for your help Tom. I didn't know that SPI communication was different from UART. Sorry about that.

[Xerxes]

I also agree that analog is suitable for drift free operation once drives are disabled while external controller is not controlling. One common way is also to control velocity via pulse trains because it produces no drift.

Using SPI would do also drift free operation but that is the most difficult way to go. For sample implementation of bit bang SPI communication to VSD drives, see Simplemotion library source code.