USB Data Acquisition?

I'm using this one, and I LOVE it! I'm very pleased with it.

No PWM, but analog out could be converted to PWM in hardware, not too easy though.

Beware, the default for the "normal" version is digital outs high when the host isn't talking to it. It's switchable, if you're up to moving a pair of SMD resistors. You can order it either way.

I'm using it for an automated battery test fixture. (robotic? :)

2&pf_id=1535

Forgive my ignorance, but what is the impact of the digital outs defaulting to high vs low?

Are there motor controllers that use analog voltage for input rather than PWM (thats wht I want PWM for)?

-C

Depends on what's connected to them. In my case, it is relays that activate on a high, and activating all the relays was a bad thing.

I had cross-lockout logic in the relays themselves that prevents it from actually happening, but it was a good thing I thought of it.. Relay A locks out the power to the coil on relay B, when A is active, and so on.

I would think so.

How about a USB to serial converter, and the microcontroller of your choice?

I'm considering designing a USB/Serial major i/o board.

I'm thinking of 32 digitial i/o, 16 ADC, plus four connectors for expansion. Each could contain a small chip/headers (one could handle 9 servos, another could give more i/o).

If there is any interest I'd consider putting it to the top of my list.

-- D. Jay Newman

Not a bad option, but in my case, I didn't want one project to turn into two. For $100, the PMD-1208LS was a no-brainer. I may even buy another one. :)

No one's done a USB to PWM motor controller yet, as far as I can tell, but it'll probably show up soon. I have thought about using a

USBMicro

401 USB I/O controller. It would feed at least 8 I/O lines to a MCU that does PWM. That MCU would in turn control the motors. Technically you don't really need a lot of speedsteps to control a motor. So one could use several I/O lines per motor to give it the speed increments. Another I/O line for the Forward or reverse modes. So you could use say 5 I/O lines to give 32 speed steps and 1 I/O line for Forward or Reverse, using up a total of 12 I/O ports off the USB device. Plus you can plug in more than one USBMicro unit to good effect if you run out of I/O ports. Since the USBMicro 401 device has SPI, one could use that interface to good effect talking with most MCU's that support SPI. I haven't tried it yet, but the SPI port might possibly work with the PAK V PWM controller, using the TTL interface. Another thought is to use a PWM controller with a USB to RS232 adapter. No fuss no mess. Just hook up your hbridges to the outputs on the PAK V PWM Controller, (although you'll need to put in some sort of a RS232 to TTL level translator to use it properly). There are several RS232 based motor controllers out there, that you could use with a USB to RS232 adapter. sells the Motor Mind units, which is one example. For myself I use the RS232 port which is talking with a ISOPOD which serves as my I/O controller. The ISOPOD does PWM like a champ. I can also use a USB to RS232 adapter to good effect here as well. But since I am planning to use a USB digital camera, which will use up a lot of the USB port's bandwidth, I am reluctant to do that. But the camera may change to firewire instead, don't know for sure yet.

"Chris H." wrote in message news:t3Dxb.17366$ snipped-for-privacy@newsread1.news.pas.earthlink.net...

How about using the USB controller to connect to a series of other chips?

For example, I like Microchip's MCP3208 ADC chip. This communicates via SPI.

For digital I/O, you could use a 40-pin microcontroller.

There are many preprogrammed chips out there (mostly PICs) which will specific things like PWM or Servo control.

Using this setup, I could see a board with: 1. 16-24 digital I/O 2. 16 channels of 12 bit ADC. 3. 18 servos 4. 8 PWM

The board doesn't seem that difficult to design; the main problem is that I'm not familiar with the U401.

-- D. Jay Newman

I am working on just this, an IsoPod under RS-232 vis USB. IsoPod

16 GPIO + plus some misc GPIO 8 ch of 12 bit A/D ( ServoPod does 16 ch ) SPI CANBUS 12 PWM 14 timer pins 80 MHZ processor, buffered serial comms.

Can decode up to 6 pairs of quadrature with the timer, or configure for PWM instance.

The PWM is capable of runing in single pin or complimentary pairs, with settable deadband and polarity.

Programmable in IsoMax, FORTH, or C.

Mike

Yup it works great. My problem was the USB digital cameras suck up most of the USB port bandwidth, so my ISOPOD is on a regular RS232 port. Using one of the Via Mini-ITX boards does make for creative I/O setups. The single RS232 port controls the ISOPOD. All those neat I/O options on the ISOPOD here. The USB port has two USBmicro U401 I/O expanders on it, plus two USB digital cameras. That gives me 32 I/O and 2 SPI's. A PCI card with two more Serial I/O ports, one of which talks to a GPS unit. The second goes to a wireless RF link to another GPS statonary unit. I am thinking about moving the cameras to Firewire instead, then using three USB to serial adapters, so I can plug in a PCI firewire card instead of the serial card, and free up the USB ports from the cameras. It would ne neat to get a Firewire, and USB 2.0 port on one PCI card too. :) I'll have to look around some more, maybe someone makes one now.

I don't know how I ever missed it before. USB and Firewire on one card.

all of a sudden there are many companies making them now.

I have used orange micro before, and am happy with them, just FYI.

Adaptec Dual-Connect in use here, works well.

My problem is that I need something commercially available, that communicates with the host via USB, and that has most of that.

One other important factor is that I need three-pin headers for all the connectors (ground, power, signal).

I may just design such a board when I have the time.

-- D. Jay Newman

Assuming the use of the ServoPod, are *all* the I/Os arranged this way?

This is part of the requirements. The headers can be either mail or femail, but all have to have ground, power, and signal.

-- D. Jay Newman

Yes, but it doesn't look like *all* the I/Os are arranged this way. Yes, the 26 servo connectors that the three connectors.

However, the ADC inputs and the auxiliary I/Os only have two-pin connectors.

-- D. Jay Newman