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PSoC 5, 3 & 1 MCU

StFa_285751
New Contributor

 Hello folks,

   

My device will be self-powered and thus will require VBus monitoring as discussed in the USB datasheet under ComponentParameters/AdvancedTab/EnableVBusMonitoring.

   

I understand the requirment.

   

What I am unsure of is the difference between the Internal and External VBus options. Both provide a pin to connect to (the host suppllied) VBus. The External option requires you to hook up that pin manually within the schematic.

   

Do they both require the resistor/cap network as shown in the diagram in the datasheet or is it just the External option? If they do then I don't understand why the two options exist.

   

Can someone give me a brief explanation as to the difference between the options?

   

Thanks,
Stephen
 

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7 Replies
ETRO_SSN583
Esteemed Contributor

This might help -

   

 

   

www.google.com/url

   

 

   

Regards, Dana.

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StFa_285751
New Contributor

 Dana,

   

Thanks, but I do understand why there is a requirement for VBus monitoring and realise that one could implement an interrupt routine manually to ensure USBFS_Stop is called if the VBus drops.

   

What I don't understand is the practical difference between the "Internal VBus" and "External VBus" options in the USBFS component.

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ETRO_SSN583
Esteemed Contributor

Not sure if this will help –

   

 

   

http://www.cypress.com/?id=4&rID=93069

   

 

   

Also in the basic ap note (AN57294) a discussion on VBUS monitoring -

   

 

   

    

   

 

   

          

   

http://www.nirsoft.net/utils/usb_devices_view.html    

   

http://www.cypress.com/?rID=70131     AN82072 - PSoC® 3 and PSoC 5LP USB General Data Transfer with Standard HID Drivers

   

http://www.cypress.com/?rID=39553     AN56377 - PSoC® 3 and PSoC 5LP - Introduction to Implementing USB Data Transfers

   

http://www.cypress.com/?rID=39404     AN57473 - USB HID Basics with PSoC® 3 and PSoC 5LP

   

http://www.cypress.com/?rID=39327     AN57294 - USB 101: An Introduction to Universal Serial Bus 2.0

   

http://www.cypress.com/?rID=40103     AN58726 - PSoC® 3 / PSoC 5LP USB HID Intermediate (with Keyboard and Composite Device)

   

http://www.element14.com/community/docs/DOC-48266/l/cypress-ce60246--application-note-on-usbuart-for...     USBUART

   

 

   

Regards, Dana.

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StFa_285751
New Contributor

Thanks Dana but I'm still no closer to answering my actual question.

   

Perhaps a direct question would serve me better:

   

If I am using the USBFS "Internal VBus" monitoring option, do I connect the associated USBFS:VBus pin directly to the USB VBus or do I have to connect it through the RC configuration shown in the USBFS datasheet under the heading "Enable VBUS Monitoring"?

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ETRO_SSN583
Esteemed Contributor

This is what the first link shows -

   

 

   

Figure 2 is a sample schematic on how to connect VBUS to a GPIO pin.

   

Figure 2. Connecting VBUS to a GPIO Pin

   

   

 

   

Regards, Dana.

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StFa_285751
New Contributor

 Hi Dana,

   

Sorry to keep getting back to you.

   

I did read that and it is similar to what's in the current datasheet. However, it seems from that paragraph that you do the same wiring for the Internal and External options so. The current USBFS datasheet words it slightly differently and makes it a bit ambiguous as to whether that circuit is for both Internal and External options or just for the External option. Perhaps I'm being over-cautious and pedantic, but after all I am an engineer 🙂

   

If they both require the same circuit, then what's the difference between the two options? (as you answered the first question you don't have to answer that one!)

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himam_31
Employee

Hi,

   

Fo External VBUS monitoring there will be a pin on the component which you need to route to GPIO in which ever way you like.On the other case the pin will be available automatically in the Pin Editor section

   

Thanks,

   

Hima

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