Feature #8
closedImplement 4 channel ADC
0%
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
Updated by foft over 7 years ago
- 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.
Updated by foft over 7 years ago
Now I have the board its clear this needs debugging.
Updated by foft over 7 years ago
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.
Updated by foft over 7 years ago
Sigh, it definitely works but if I read say channel 1 - I still receive input from the other channels
Updated by foft over 7 years ago
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!
Updated by foft over 7 years ago
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!
Updated by foft over 7 years ago
- 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.