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Use of adc channel 3 on BOE — Parallax Forums

Use of adc channel 3 on BOE

borisgborisg Posts: 39
edited 2013-07-08 10:48 in Propeller 1
Not sure if this has been dealt with earlier, but there seems to be a discrepancy between the documentation for PropBOE adc and the schematic for BOE. In the PropBOE adc documentation there's a comment that adc channel 4 is connected to the on-board electret microphone through an amplifier. However, no such connection exists in the schematic and the microphone is connected to the Prop using the 2 pin sigma/delta converter. In case this was an undocumented feature, I hooked up a scope to adc channel 3 and no activity was noted yelling at the BOE.

So, I'm assuming the schematic is correct but am just curious if adc3 was at one time connected to a microphone input? I need all 4 A/D channels for my project as it suddenly occurred to me that I should use one of them to monitor battery voltage.

Comments

  • PublisonPublison Posts: 12,366
    edited 2013-07-08 10:04
    borisg wrote: »
    Not sure if this has been dealt with earlier, but there seems to be a discrepancy between the documentation for PropBOE adc and the schematic for BOE. In the PropBOE adc documentation there's a comment that adc channel 4 is connected to the on-board electret microphone through an amplifier. However, no such connection exists in the schematic and the microphone is connected to the Prop using the 2 pin sigma/delta converter. In case this was an undocumented feature, I hooked up a scope to adc channel 3 and no activity was noted yelling at the BOE.

    So, I'm assuming the schematic is correct but am just curious if adc3 was at one time connected to a microphone input? I need all 4 A/D channels for my project as it suddenly occurred to me that I should use one of them to monitor battery voltage.

    Do you have a reference to the offending document. The current document seems to be correct.
  • borisgborisg Posts: 39
    edited 2013-07-08 10:15
    The origin of the supposed use of chan3 is at:
    http://learn.parallax.com/node/103

    There's been no update for over a year of that page.
  • borisgborisg Posts: 39
    edited 2013-07-08 10:16
    Sorry, hit post too fast. The reference to the use of the A/D channel is in the source code for PropBOE adc.spin
  • PublisonPublison Posts: 12,366
    edited 2013-07-08 10:48
    borisg wrote: »
    Sorry, hit post too fast. The reference to the use of the A/D channel is in the source code for PropBOE adc.spin

    I believe I sent this information to Parallax from a previous thread. Will have to double check.

    http://forums.parallax.com/showthread.php/148284-NEWBIE-Needs-info-for-additional-A-to-D-inputs.?p=1187382#post1187382

     It does look like PropBoe adc.spin has an erroneous entry in lines 101-104. Good catch!

    You should email tech support with the problem from this page:

    http://www.parallax.com/Support/SupportHome/tabid/474/Default.aspx
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