Minima schematics understanding

Hardware UNO R4 UNO R4 Minima
1

Hello All.
I'm trying to understand why arduino put tension bridge on pins 16 and 49 on the renesas uC.
By calculation, we have 3.3V on pin 16 and 0.6V on pin 49

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https://docs.arduino.cc/resources/schematics/ABX00080-schematics.pdf

For pin 16 we have

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For pin 49 we have

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image930×162 16 KB

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So I guess, pin 16 bridge is for ADTRG0 ?

Asynchronous trigger from the external trigger pin, ADTRG0.

And the 49 is for CMPREF1 ?

ACMPL function, reference voltage input pin ?

I want to know what's the aim of adding these tension bridge.
Thanks

RA4M1 full datasheet

2

nobody knows ? :sweat_smile:

3

It's not been a whole day yet - be patient!

4

pin16 is also USB_VBUS pin. Should be connected to VUSB.

Datasheet says: "USB cable connection monitor pin. This pin should be connected to VBUS of
the USB bus. The VBUS pin status (connected or disconnected) can be
detected when the USB module is operating as a device controller."

pin49 gets about 0.6V by divider. looks like a reference voltage as you think.

i would like to know aim of these designs too.

5

I also read it, so for me, it is not obligatory to connect it to VBUS, only if you want to know in your program if there is or not a usb connected.
Not obligatory confirmed by the fact that arduino haven't connect this pin to the VBUS...

6

I suspect that for the P407 USB_VBUS input that there is some Renesas USB code module that needs to read that pin status as a 1, see datasheet for the register it crops up in.

Which could be either in normal use, or for board testing during manufacture.

27.2.13 Interrupt Status Register 0 (INTSTS0)

  b7 VBSTS VBUS Input Status 
    0: USB_VBUS pin is low
    1: USB_VBUS pin is high.

 b15 VBINT VBUS Interrupt Status 
   0: VBUS interrupts are not generated
   1: VBUS interrupts are generated.

... but I could be backing up the wrong tree! :slight_smile:

7

okay. Thank you for your response.
So I think, to be sure, the best thing is to remove R7 and R8 resistors and see what happens to usb ha ha.
I'll try it when I get a minima.

8

Further on the P407 USB_VBUS input.
Okay, so these are the USB registers of interest:

USBFS_SYSCFG  - 0000010000010001  // System Configuration Control Register
USBFS_INTENB0 - 1101111100000000  // Interrupt Enable Register 0

The USBFS_SYSCFG tell us in addition to being enabled, that bit b4 is high:

b4 = DPRPU - D+ Line Resistor Control - 1: Line pull-up enabled.

... which is as might be expected.

More interesting is USBFS_INTENB0 for which ALL but one of these defined interrupts are enabled; this includes the VBUS one:

b15 = VBSE - VBUS Interrupt Enable - 1: Interrupt output enabled

So no need to remove any resistors, they are there for a reason! :slight_smile: