To answer your question, yes, we are using the D/A outputs from the PC-104 CPU/A-to-D board combo as inputs into voltage comparators with their other pins driven by a simple sawtooth waveform generator which is then converted into a 3KHz DC pulse train of varying duty-cycle.
Yes, you could use a totally digital PWM solution, but this solution uses a very minimal amount of easy-to-get parts and has a very limited number of connections between the Interface Board and the PC-104 CPU card. If you're interested, I'll gladly send the schematic for the circuit your way. --- John Carmack <[EMAIL PROTECTED]> wrote: > At 10:44 PM 3/13/2003 -0800, you wrote: > >Gizmocopter Work Session Notes for March 13th, 2003 > > > > > >The Gizmocopter work session began at 7:00PM. > Chris, > >Bill, David M., Nate, Sean, Michelle, Sarija, and > >several cats and a dog were in attendance. Dinner > >consisted of lazagna, and was delicious. The > >Gizmocopter work session was somewhat muted tonight > as > >most efforts have come to a standstill until the > >Interface Board -- a PCB housing power, control, > and > >analog interfaces -- is complete. The board will > be > >home to a 5VDC power converter, analog to PWM > >converters for the primary motor drive circuits, > and a > >general connector interface for the > gyro/accelerometer > >array/cube for Gizmocopter's IMU function. Chris > >showed the two 2-axis, 10g, accelerometer chips > that > >he acquired from Analog Devices. Additionally, > two > >more Analog Devices gyros (ADXRS150ABG) were > purchased > >for Gizmocopter's IMU during the meeting. We now > have > >parts. Now if we can only get boards... > > A few points: > > I am looking forward to hearing how the Analog > Devices gyros work out. > > The IMU functionality should communicate with the > CPU over a serial line if > possible, so it can be tested on desktop computers > as well as the flight > computer. If you are just using an existing A/D > board on the CPU, it > probably isn't worth adding another controller for, > but I have often found > it very handy to test IMU things on a desktop > computer. > > The accelerometers are useful as an inclinometer for > initialization of the > gyros, but you can live without them if you have a > level launch pad. Don't > expect to be able to integrate accelerometers and > gyros for accurate 3D > positioning for hovering or auto-land. Even the > much more expensive ones I > use aren't up to that task at the few-feet precision > level that is needed. > > Analog to PWM? Does this mean that the flight > computer is using a D/A > board to generate an analog signal for throttle > level, which is being > converted back to a digital pulse train for the > motors? > > John Carmack > > > > _______________________________________________ > ERPS-list mailing list > [EMAIL PROTECTED] > http://lists.erps.org/mailman/listinfo/erps-list __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - establish your business online http://webhosting.yahoo.com _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
