[Milkymist-devel] proposed insertion/detection for audio line in/out (was Re: J3 redesign for rc4)
adam at sharism.cc
Mon Feb 13 23:13:38 PST 2012
To let M1 have awareness of plugging audio line in/out connector,
followings are proposed idea and combined earlier suggestions from you. A
latest draft schematic:
1.) add one pullup 100K Ohm R233 to 3.3V and connects to J2:3 pin,
2.) name a new net LINEOUT_DET and connects to both J2:3 and fpga.
so this detective pin is under Normal = Low (0.303V), Plug-in = High level
1.) add one pullup 100K Ohm R25 to 3.3V and connects to J1:3 pin,
2.) name a new net LINEIN_DET and connects to both J1:3 and fpga,
3.) add back R23, R24 6.8K Ohm in previous version and connects them to
AUDIO_AGND. So it's under Normal = Low (0.395V), Plug-in = High (3.3V) level
VIL(V, max) for low detection, according to table 9 on page 10 of
which is safe.
On Wed, Feb 8, 2012 at 5:33 AM, Joerg Reisenweber <joerg at openmoko.org>wrote:
> Hi Adam,
> Yes, this looks pretty decent, the schematics (p.1) as well as the selected
> varistor which is a nice component and perfectly suited to replace the
> As there's always sth to improve :-) I suggest:
> cut J1:3<->2, connect J1:3<->1
> cut J1:5<->4, connect J1:5<->1
> rationale: connect unused input to GND -> less noise
changed on J1:5, but also applied plug detection on J1:3 as above.
> cut connection and insert a 100R, from joint C19*R17 <-100R-> J2:2,3
> cut connection and insert a 100R, from joint C21*R18 <-100R-> J2:4,5
> Rationale: some protection for LineOut amp / internal clamp diodes there
100R added, and there are no clamping diodes in the fpga. I edited two
varistors in advance there line-out path, how do you think ?
> consider 2pin with jumper to GND for TP50
> rationale: again noise of unused input
limited to present crawl space around U1 and new proposed U-Shaped
expansion board coming up which will at exactly the upper area of U1
too. We'd just keep those footprints of DC block caps. instead of 2pin
headers or test points.
Hopefully comments feedback when you're available. Thanks. :)
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