Pwmpal question

Tibo

Hello all,

I want to drive the 'Cybot' H-Bridge using a PWMPAL.
My question is :

In order to save some I/O ont my BS2e (not OEM, standart), can I use the PWMPAL alone (not under the BasicStamp, but side by side), and if yes what wiring shall I do ?

Ialready thought of natural answer : if not used all I/O of the PAL are set as inputs...BUT this does not solve my lack of I/O ont he stamp since I'd like to use 4 of the PAL output AND all the stamp I/O.

So i'd wire only the P0 pin from the Stamp to the PWMPAL, but I dont know about power and electrical issues...

Can you help ?

Thank you

Post Edited (Tibot) : 10/10/2005 8:24:08 AM GMT

Tibo

Aarg, nobody knows and I cant find the information on the parallax web site [noparse]:([/noparse]

Nobody ever took the PWMPAL aside from the BasicStamp ?

Tracy Allen

Yes, you should be able to run the PWMPAL on its own, only with the following physical connections:
pin 5 to pin 5 (p0 for data)
pin 4 to pin 4 (Vss, ground)
pin 23 to pin 23 (Vss, ground)
pin 21 to pin 21 (Vdd, +5 volts)
The connections to Vss and Vdd would not have to be made right on the corresponding Stamp pins. You could find those voltages elsewhere in your system.

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Tracy Allen
www.emesystems.com

Tibo

·cool !

Thank you Tracy !

Tibo

Well...doesnt workin in fact
I tried, re-tried, did a first pcb, then a second...then I checked if pwmpal was not dead ( ) wasn't.
Can't make it run side to side to the BS2...

Dont you think it needs the Vin(p13) pin connected also ?

Thank you !

Jon Williams

I haven't used the PWMPAL in a long time so I had to go hunting for one -- and I have good news.

First, you're using the PWMPAL differently than we designed it, so be very careful.· Next, you need to make these connections:

- Vdd
- Vss
- Rst
- Sio

The attached diagram shows where the connections are on the PWMPAL.· I suspect you neglected the RST line and I confirmed that if this is not connected (I popped my PWMPAL into the breadboard of a PDB) then there is no communication between the devices.· Note that any of the pins on the PWMPAL that have no names are just blank sockets.

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Jon Williams
Applications Engineer, Parallax

Tibo

As you noticed, electonic is new to me and for now I'm practicing ironing, pcb'ing and patience !

Thank you for the hunt Jon , I really appreciate the time and energy you spend supporting us.

Tibo

A (probably) last question to make sure : can I let the RESET pin of the PWMAL floating ? Or do is it mandatory to connect it with the RESET pin of the BS2e ?

Thank you.

Jon Williams

If you let it float, it won't work -- I mentioned that earlier. Since you're new (you said so), I suggest you stop *cheating* (or trying to) and make the connections as they are designed to be made; that will eliminate any further troubles.

Connect: Vdd, Vss, Rst, and Sio to the BASIC Stamp so that the software demos we provide will work. And you'll be on to writing code instead of troubleshooting hardware -- that's much more fun!

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Jon Williams
Applications Engineer, Parallax

Tibo

I already followed your initial advise (stop *cheating* (or trying to) and make the connections as they are designed to be made) but i got short on free pin....this is why all this *cheating*.
Thank for all Jon !