[Mezzanine] Sensors board Rev B - call for review

Grant Likely grant.likely at linaro.org
Tue Oct 20 23:17:42 UTC 2015


For reference, here is a
​rendering
 of what the board looks like. I've already swapped out the connector for
the through-hole stackable one.
​ I've not changed the IO voltage selection.

g.​

​[image: Inline image 1]​


On Tue, Oct 20, 2015 at 9:16 PM, Yang Zhang <yang.zhang at 96boards.org> wrote:

> + mezzanine review mailing list.
>
> On 20 October 2015 at 21:11, David Mandala <david.mandala at linaro.org>
> wrote:
>
>> Grant,
>>
>> Nice work. :-D Comments below.
>>
>> David
>>
>> On 10/20/15 2:28 PM, Grant Likely wrote:
>>
>>> I've completed rework, layout and routing of the Rev B Sensors board,
>>> and it is now ready for review. I've attached the new schematic and
>>> new component placement diagram. The design files have been pushed out
>>> to the "rev-b" branch on github and git.linaro.org:
>>>
>>>
>>> https://git.linaro.org/people/grant.likely/96boards-sensors.git/shortlog/refs/heads/rev-b
>>>
>>> It is ready for review, and very close to being ready for
>>> manufacturing. However, I have some questions that I would like some
>>> feedback on. Help and suggestions are greatly appreciated.
>>>
>>> First, here are the things to notice on the new design:
>>> - Arduino connectors have been centered and lined up on the bottom edge
>>>
>>> of the board, including the SPI header. This should make it compatible
>>> with more Arduino shields
>>> - More grove connectors have been added as well as more 96B IO.
>>>    - Bottom edge uses right-angle SMD grove connectors to avoid
>>> shorting against the USB ports on the baseboard.
>>>    - GPIO A-F are all level shifted
>>>    - SPI has been brought out to P7
>>>    - Arduino Grove connectors match naming convention of Arduino Grove
>>> shield (D3-D7, A0-A2, I2C). The Arduino Grove examples should now work
>>> without any changes.
>>> - Grove connectors are evenly spaced on either side of the Arduino
>>> headers
>>> - A CBUS connector has been added for 1.8V IO controlled from the USB
>>> port. This will be an undocumented feature allowing the FTDI to be
>>> used to control boot select pins on the base board, but requires the
>>> signals to be manually wired up (hence I'm not going to document it -
>>> It will just cause confusion)
>>> - J1 added to support manufacturing test. It allows the Arduino to be
>>> reset from the FTDI
>>> - I2C0 & I2C1 have stronger pull-ups on the data and clock lines.
>>>
>>> Questions:
>>> 1) Are the Grove connectors too close together. I tried to give lots
>>> of space so that labels can be easily read, but there isn't much room
>>> between the mounting holes. I could have more space if I dropped two
>>> Grove connectors and put more space between P14,P15,P17 and
>>> P11,P10,P9.
>>>
>>
>> Space wise it looks good just as it is.  All of my grove cables fit
>> internally to the connectors, and I can read the labels with no issues.
>>
>>
>>> Q: Which is better. The current layout, or dropping 2 Grove connectors
>>> and spacing them out more.
>>>
>>
>> In this case more is better so I think keep it the way you have it now.
>>
>>
>>> 2) The LS expansion connector is currently an SMD pin header on the
>>> bottom side. Seeed has sourced a through-hole stackable connector that
>>> I could use instead
>>>
>>> Q: Is it worth replacing the SMD pin header with a 2x40 stackable header?
>>>
>>
>> Yes it's worth it, stack-able gives a Maker or Developer access to all
>> the signals and power out not just what you bring out and there are 5 pins
>> you don't bring out.  The cost is comparatively minimal but allows full
>> access or stack-ability if needed.
>>
>> We should also make sure those through-hole stackable connectors are
>> available for sale at Seeed Studios. I have at times added a stackable
>> connecter with an rPi just to increase the spacing between the rPi and an
>> expansion board.
>>
>>
>>> 3) The board has a solder bridge jumper (QS1) for selecting between
>>> running the IO at 3.3V and 5V. 5V is the default for compatibility,
>>> but someone who knows what they are doing can switch the solder bridge
>>> to run at 3.3V for everything. (Most sensor devices appear to be 3.3V
>>> these days. The ATMEGA will happily run at either 3.3V or 5V)
>>>
>>> Q: Is a solder jumper the best way to select the voltage level? Or
>>> should I put a physical switch on the board?
>>>
>>
>> Personally I'd use a 3 pin jumper, pin 1-2 is 3.3VDC operations, pin 2-3
>> 5VDC operations.  My second choice would be a switch.  Last choice would be
>> a solder bridge, you might be surprised how many people shy away from a
>> soldering iron.
>>
>>
>>> Thanks in advance,
>>> g.
>>>
>>>
>>
>> --
>> David Mandala <david.mandala at linaro dot org>
>> http://www.linaro.org/ Public Key id: 45B2D952
>> Murphy TX, 75094 +1.972.891.8436
>>
>>
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>>
>
>
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