Re: PWM Testing Equipment
 

This is great... but old computers are hard to find that still work properly... It would be nice to rig up a newer interface in lieu of the RS-232 (as much as I loved that). Perhaps Ethernet port or USB (e.g. FTDI driver)... that would make it possible to work for the classmate PC. The classmate is small and should have a powerful enough processor to be quite useful. I'll bet there are teams out there that have classmate PC's. ;)

Re: PWM Testing Equipment
 

If you put the word out that you're interested, they'll come out of the woodwork.

Every junker PC that's been given to me (well over a dozen so far) has had no trouble being used for test equipment like this.

RS232 is easy to work with because it has control pins (outputs) that are independent of the serial data lines, and which are easily turned on or off with one register write (2 machine code instructions).

I've not studied the USB or Ethernet* port. Find me a technical document which has detailed instructions how to toggle control pins at the bare-metal level on those and I'll look at it.


*Decades ago, I wrote a letter the editor of Digital News magazine correcting an error in an article they published about the Ethernet collision avoidance/detection/recovery protocol. I got a phone call from the editor asking me if I was involved in any way in the development of the protocol. Unlike a certain politician whom I will not name here, I said no. They published my letter, but appended to it a note that I was not the inventor of the Ethernet.

Re: PWM Testing Equipment
 

The dozens I've had mostly all worked when I got them, but time takes it's toll....I recently got rid of about three or four dozen, and at least half of them were dead, usually having issues with disk drives. I'm down to fewer than 50 computers now.

Sadly, this old stuff is going away. It was so nice to be able to do so much with so little "investment".

Re: PWM Testing Equipment
 

I've got a couple like that.

If they've got a USB port (and BIOS boot support for it), they don't need a disk drive to run FreeDOS, or even Linux :-)

Re: PWM Testing Equipment
 

Most of mine didn't have USB....pre-'96

Re: PWM Testing Equipment
 

Yeah, I've got a few of those too, with bad hard drives.

I use a 1.44MB 3.5" diskette, with bootable FreeDOS.

FreeDOS fits on there with space to spare for TP7 and apps. And you can use the memory for a RAMdisk or cache.

Re: PWM Testing Equipment
 

The 360k 5.25" floppy drives are dying fast too....

Re: PWM Testing Equipment
 

I've got only one good one left, and a box with 500 old disks :-(

Re: PWM Testing Equipment
 

5.25" disks must hold a lot of data. I bet with 2 of them you wouldn't even need a hard drive. :D

Re: PWM Testing Equipment
 

I'll second this. When I was still a teacher a few years ago, I was given a couple Pentium 2s that were "broken". I figured it would be fun for kids to open up and see whats going on. Word got out and I ended up with 6-7 P2/3s just from around the building. I did nothing to these other than load ROBOlab (the RCX LEGO software) and arduino onto whatever windows they had on them. They worked great up until an administrator threw them away. Now I'm extra mad after learning of this great additional use for them. However, I'll just be putting out the word that we're looking for donations again, and I'm confident we will have no problems.

Hopefully people think I'm sitting here working hard and the random lol is just because I'm a bit off...

Also, this is the first time I've wondered about the etymology of ethernet???

Re: PWM Testing Equipment
 

Hmmmm... perhaps instead of going that route maybe this would work:

http://gridconnect.com/usb-to-serial...32-to-usb.html

Re: PWM Testing Equipment
 

2nd paragraph, first page:

http://ethernethistory.typepad.com/p...ernetPaper.pdf

Re: PWM Testing Equipment
 

Two things:

1) The $80 price tag kind of defeats the purpose

2) USB does not have any control outputs, just data.

Re: PWM Testing Equipment
 

I just got a radio shack version of this velleman kit. USB interface for several I/O options and it mentions PWM output too. The local RS had a sale on it so your availability may vary. RS site doesn't list it but there is a kit that does DC to PWM. It doesn't appear to be available at a store near me. I may risk being on the RS mailing list forever by ordering it online.

Re: PWM Testing Equipment
 

If you've got an old IFI robot controller sitting around and the Microchip C18 build tools, you could modify code I wrote to do both jobs. The code in frc_pwm.zip will generate a very precise servo PWM signal, and the code found in ifi_ir_sensor.zip will show you how to determine the servo pulse width. The code I wrote for the 2004 game does kinda the same thing.

-Kevin