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Smart Bluetooth Forum Discussions

Anonymous
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Hi,

We designed our board targeting the BCM20732S, but have now populated it with a BCM20736S part. I thought they were direct pinout equivalents, but after double checking I found two differences.

BCM20732S        -> BCM20736S

Pin 10 = BT_ANT -> Pin 10 = RESERVED (Leave floating)

Pin 38 = GND      -> Pin 38 = NC

Pin 10 is already floating on our schematic, but pin 38 is tied to ground in our schematic. Will connecting pin 38 to GND on a BCM20736S device cause any issues?

Thanks,

Briana

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1 Solution
MichaelF_56
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On all of the 2073XS devices, Pin 38 is not connected to the die internally, so we updated the datasheet to state NC vs. GND.

Pin 10 used to state 'External Antenna' because it connects to the onboard antenna, but that confused people and they thought they could add their own antenna to this pin, so we changed it.

View solution in original post

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MichaelF_56
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On all of the 2073XS devices, Pin 38 is not connected to the die internally, so we updated the datasheet to state NC vs. GND.

Pin 10 used to state 'External Antenna' because it connects to the onboard antenna, but that confused people and they thought they could add their own antenna to this pin, so we changed it.

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Anonymous
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Hi,

I see the update to the pin 10 of the BCM20732S from BT ATN to Reserved. However, in what looks like the latest RM (MMP20732S-TRM103-R) pin 38 is still shown as GND.

Is it correct to assume it is safe to connect Pin 38 to GND, rather than NC, on all 2073xS devices, since it's not connected to the die internally?

Thanks,

Briana

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I think this is a safe assumption.

I checked the module datasheet for the 20732S and it appears to be correct for pin 10: BCM20732S Bluetooth Low Energy SiP Module Data sheet

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Anonymous
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I agree that pin 10 was updated to be Reserved, but pin 38 shows as GND still. I've talked to the team here and we don't anticipate going back to the BCM20732S, we're going to be sticking with the BCM20736S, so since we're getting ready to spin our board anyway I'll just make pin 38 NC.

Thanks,

Briana

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I just realized that I changed this in the 20736S datasheet, but not the 20732S version.  I will work with Tech Pubs to update the document now.

Thanks for pointing this out.

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Anonymous
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Thanks for the clarification.

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Anonymous
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Hi mwf_mmfae,

I'm confused by this thread.  I'm trying to use P38 as SPI MOSI on the BCM20736S module and it's not working.  I can't even get P38 to function as a GPIO output.  It's deader than a doornail.  On the other hand, using the TAG board which contains a BCM20737 chip, I AM ABLE to use P38 as both MOSI and GPIO (not at the same time of course) USING THE EXACT SAME SOFTWARE.

Reading this thread I see there is something up with P38 but I can't quit figure out what it means.  What is meant by P38 is "not connected to die"?  Does this apply to the 726S module?  You said something about marking it as NC but I looked in both the TRM and the Datasheet and I don't see NC in there anywhere. On the contrary it indicates that P38 is available (but paired with P14... and yes I did disable both input and output on P14).

Thanks for any clarifications and any help you can provide on P38 in the 736S module.

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ehoffman,

This thread is referring to physical pin 38, not logical P38, which is a firmware reference designator.

Physical pin 38 is not connected to the die.

Logical P38 can be used as the MOSI function on SPIFFY 2 per the WICED™ Smart Hardware Interfaces

Note that per this blog: BCM2073XS GPIO Basics

Since the 32 pin package (SoC) and the modules are pin-limited, some of the logical GPIOs are multi-bonded before bringing them out on the balls on the chip.

For the 32 pin package used within the SIP modules, the following are bonded in this manner:

  • P8 and P33
  • P10, P11, P27 and 32 KHz xtal in
  • P12, P26 and 32 KHz xtal out
  • P13 and P28
  • P14 and P38

Note here that you can use only one of the GPIOs (or its alternate function) from each of the rows above. The other unused GPIO from that row should in general be input/output disabled (especially when it is an input).

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Hi mwf_mmfa,

If none of the logical pins in a group of bonded GPIOs are used, for example if neither P14 nor P38 is used, is it suffice to disable them programmatically and leave the physical pin no connection?

BR,

Wataru Sugimoto

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First off, make sure you review the updates to the dual bonded pins I created here last week: BCM2073XS GPIO Basics

You should be fine leaving these pins NC when unused.

Thanks for your response and the blog post.

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