I just got an INEX ZX-SERVO16U, which is basically a 16-servo controller that comes with a USB-to-serial cable. It appears to be very similar to the Parallax Servo Controller, and comes with a CD containing the Parallax PCSI software for Windows.
Connecting to the controller isn’t hard at all - I plug it in, I get the prolific usb to serial chipset detected, and I have a /dev/ttyUSB0 I can talk to. I have a C++ program (adapted from another one I wrote to talk to an iRobot Create) which handles the basic commands.
When I use the board connected to a Windows machine using PSCI, the three servos I have connected work fine. When I connect to a small board running a Linux 2.6.21 kernel, I can communicate with the board but it doesn’t always activate the servos. Although the board takes an external 6V power supply, I thought it might have a higher-than-normal current requirement from the USB port, and sure enough it appears to take the 5V line from the USB interface in addition to the TX, RX and GRND outputs of the Prolific USB to serial converter it’s using.
Sometimes I can get the servos to respond after resetting (only by pushing the reset button - the reset command doesn’t do the trick).
The documentation from Inex isn’t that helpful and neither of their websites (inex.co.th (Thai) or inexglobal.com (english)) seem to have any information about this product at all.
Interestingly it looks like Parallax has also discontinued their older serial-based servo controller board, so I might have to go with the newer Parallax Propeller server controller, which is supposed to have open source support.
There are two possibilities here: 1. the PCSI software is using some method for communicating with the device that works more reliably than what I’m using, or 2. I haven’t solved the power problem adequately.
For power I’m using a 25W 5V DC-DC switching regulator set to output 5.9V.
Any suggestions on where I can go to find more info would be welcome.