Sampling multiple AD inputs Coding Help - Page 2 - Electronic Circuits Projects Diagrams Free

Darth Bagel · 5th February 2008, 10:53 PM

Not strictly speaking at the exact same time, but I see no reason why you couldn't get close enough, if you had enough pins.

dknguyen · 5th February 2008, 10:55 PM

Quote:

Originally Posted by Kryten

bananasiong is it possible to sample two signals from external ADC at the same time on a PIC18XXXXXXX?

You can if the ADC supports it. You won't be reading them into the PIC simultaneously though unless it has some crazy parallel or multi-serial interface (but you probably don't need to anyways).

A dsPIC for example has multiple sample-holds for it's ADC. It can capture all the samples at the same time but only uses one SAC register to convert them. So it samples them all at the same time, but only converts (ie. reads them) them sequentially. THey are all sampled at the same point in time though.

bananasiong · 6th February 2008, 02:51 AM

You don't need external ADC, just switching between two channels if time is allowed. Or if you want PIC18F2331 (or the same family) has two sample and hold which allow you to sample two channels simultaneously. But the conversion time channel by channel. It has 4 level FIFO so you don't have to worry about the data loss.
Depends on your sampling frequency, if you don't need that fast, just PIC16 will do by switching the channels.

Kryten · 6th February 2008, 08:49 AM

Well im going to have at least 10 samples/sec (maybe more) so it will probaly be enough with a PIC16..

**Nigel Goodwin** · 6th February 2008, 09:26 AM

Quote:

Originally Posted by Kryten

Well im going to have at least 10 samples/sec (maybe more) so it will probaly be enough with a PIC16..

10 samples per second is a nice easy slow rate, easily done.

Kryten · 6th February 2008, 09:29 AM

So i can just use the one AD inside and plex my way from one to the other?

bananasiong · 6th February 2008, 09:40 AM

Yeah just switch to different channel as you want.

**Nigel Goodwin** · 6th February 2008, 09:40 AM

Quote:

Originally Posted by Kryten

So i can just use the one AD inside and plex my way from one to the other?

Yes, exactly as it's designed to do (and as, as far as I know, all other A2D's are).

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5th February 2008, 10:53 PM	(permalink)
Darth Bagel	Not strictly speaking at the exact same time, but I see no reason why you couldn't get close enough, if you had enough pins.

6th February 2008, 02:51 AM	(permalink)
bananasiong	You don't need external ADC, just switching between two channels if time is allowed. Or if you want PIC18F2331 (or the same family) has two sample and hold which allow you to sample two channels simultaneously. But the conversion time channel by channel. It has 4 level FIFO so you don't have to worry about the data loss. Depends on your sampling frequency, if you don't need that fast, just PIC16 will do by switching the channels. __________________ Superman returns..

6th February 2008, 08:49 AM	(permalink)
Kryten	Well im going to have at least 10 samples/sec (maybe more) so it will probaly be enough with a PIC16.. __________________ Simplicity rules Good enought - its perfect ?? 2 Gig of free online backup space Are you a Chemist?

6th February 2008, 09:29 AM	(permalink)
Kryten	So i can just use the one AD inside and plex my way from one to the other? __________________ Simplicity rules Good enought - its perfect ?? 2 Gig of free online backup space Are you a Chemist?

6th February 2008, 09:40 AM	(permalink)
bananasiong	Yeah just switch to different channel as you want. __________________ Superman returns..