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Some basic questions — Parallax Forums

Some basic questions

nisbusnisbus Posts: 46
edited 2010-03-25 00:08 in Propeller 1
Hi,

I have a few basic questions about the Propeller chip.

1. I see in the objects exchange that there are a number of objects for doing analog to digital conversion using ADC0831 so I wonder if the Propeller isn't capable of doing analog to digital conversions by itself?

According to the manual on CTRA and CTRB it states that with a little configuration these could be used for ADC but it fails to mention what kind of configuration that would need.
Can anyone shed some light on that?

2. I have a USB datalogger #27937 which I haven't been able to get to detect a thumb drive yet but I'm wondering how I could connect the propeller to a PC using USB?
The datalogger is probably not the way to go since all the objects I see for that create files to log to while I would like to write a driver on the PC to decipher the data coming in from the propeller (I have a Tri-Axis accelerometer #28026 which I have gotten to work but I'd like to output the values to my PC).
How are people getting data from the propeller to their PCs (bluetooth would be cool)?

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Thanks,
nisbus

Comments

  • kwinnkwinn Posts: 8,697
    edited 2010-03-24 02:54
    The prop can use 2 pins to perform analog to digital conversions. There are objects in the obex with the programs and explanations.

    The simplest prop to PC transfer method would be to use the prop plug and one of the serial objects from the obex to send the data to a terminal program (PST) or other data logging program on the PC.
  • Kal_ZakkathKal_Zakkath Posts: 72
    edited 2010-03-24 03:23
    kwinn said...
    The prop can use 2 pins to perform analog to digital conversions. There are objects in the obex with the programs and explanations.
    Are there? I had a quick look for 'ADC' in the obex but didn't see any.

    Anyway, you might want to check out the application note on counters:
    http://www.parallax.com/tabid/442/Default.aspx·("AN001 - Propeller Counters")

    Can't check since I'm at work but going from memory (it should all be in the app note anyway):

    You need two pins, two capacitors, and two resistors (values in the app note).
    I think it uses both A and B counters for a cog, and will give you 12 bit resolution.
    The main caveats are that the capacitors should be within one inch of the prop chip, and the circuit will not work on a breadboard (I believe this is due to the breadboard's own capacitance)
  • Nick McClickNick McClick Posts: 1,003
    edited 2010-03-24 03:31
    Take a look at the microphone demo in the Propeller tool as an example of how to do Sigma Delta with the prop - I don't know if there are any good objects, though.

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  • KyeKye Posts: 2,200
    edited 2010-03-24 05:13
    There are alot of ADC objects avialable online... Though most use external ADCs.

    Here's my audio ADC driver which uses the counters.

    http://obex.parallax.com/objects/566/

    Its made for high speed audio sampling, so the interface does not allow you to get just one sample at a time.

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    Nyamekye,
  • nisbusnisbus Posts: 46
    edited 2010-03-24 23:57
    Thanks all for your comments.

    I'm thinking that I'll go with an external ADC.

    One thing that occurred to me is the usb port I use to program the demo board with, can that be used as an output as well (can I send data to the PC from that)?

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    Thanks,
    nisbus
  • KyeKye Posts: 2,200
    edited 2010-03-25 00:08
    Yep,

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    Nyamekye,
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