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Feature #8

closed
AD FO

Implement 4 channel ADC

Feature #8: Implement 4 channel ADC

Added by admin over 8 years ago. Updated over 8 years ago.

Status:
Closed
Priority:
Normal
Assignee:
foft
Start date:
04/04/2017
Due date:
% Done:

0%

Estimated time:

Description

The one channel ADC on the v1 board is replaced by a four channel one on the v2 board.

Modify the implementation to support this

Files

adc084s051.pdf (1.27 MB) adc084s051.pdf foft, 05/11/2017 08:26 PM

FO Updated by foft over 8 years ago Actions
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 #1

  • Status changed from New to In Progress

Written initial support based on data sheet and simulated. Not yet built into test core or tried on real hardware.

So far all four channels sampled, but only SIO input connected to core.

FO Updated by foft over 8 years ago Actions
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 #2

  • Tracker changed from Bug to Feature

FO Updated by foft over 8 years ago Actions
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 #3

  • Assignee set to foft

FO Updated by foft over 8 years ago Actions
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 #4

Attached ADC data sheet

FO Updated by foft over 8 years ago Actions
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 #5

Now I have the board its clear this needs debugging.

FO Updated by foft over 8 years ago Actions
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 #6

Debugged and now working.

PBI and SIO audio will be mixed. For now I'm not feeding MIC_L and MIC_R anywhere - these will be connected to some sampler register. I guess D500 and D501 if the 'replay cartrige mode' is enabled.

FO Updated by foft over 8 years ago Actions
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 #7

Sigh, it definitely works but if I read say channel 1 - I still receive input from the other channels

FO Updated by foft over 8 years ago Actions
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 #8

Pretty sure this is down to floating inputs. Since there is no driver and low capacitance the input picks up the previous sample stored in the ADC. I checked this out by trying two approaches:
i) Sample a single channel and checking for no crosstalk
ii) Grounding the floating inputs and checking nothing sampled

I also tried out deselecting ADC between frames in case that helped. It didn't, just decreased the same rate a little!

FO Updated by foft over 8 years ago Actions
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 #9

So I guess we should have some more passive components here. On the other hand I'm kind of attached to SIO noise down to cable interference. If we fix this too well we may lose that!

FO Updated by foft over 8 years ago Actions
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 #10

  • Status changed from In Progress to Closed

Closing since the core support is in place. Noise reduction and sampler connection may be raised as future feature requests.

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