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PSoC 4 MCU

paroc_1316856
New Contributor II

In KBA210620 you say that 22Ohm resistors should be placed in series with the D+ and D- USB data line but the technical reference manual specifically says that the silicon has 22Ohm resistors internal to the chip:

18.1 Features
The PSoC USB has these features:
...
■ Integrated 22  USB termination resistors on D+ and D– lines, and 1.5-k pull-up resistor on the D+ line

Do I need external 22Ohm resistors as well?

KBA210620 also says that 0.1uF should be connected between VBUS and GND. Is this necessary even if VBUS is just used to sense the presence of the host, and enable the USB drivers? There is no reference to this in the trm.

I am having problems getting the USB to work reliably. It works as long as there is at least one USB hub between the PSOC and host controller on the PC, but not if the PSOC is connected directly to the host controller, either USB3 or USB2. Error message is : "USB device not recognised, the last device connected to this computer malfunctioned and windows does not recognise it" with device manager saying "Windows has stopped this device because it has reported problems. (Code 43). A request for the USB device descriptor failed."

Traces on the PCB between USB connector and PSOC are about 5mm in length, matched to about 0.5mm,  and reasonably matched to 100 Ohms. PSOC is self powered.

 

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1 Solution
paroc_1316856
New Contributor II

Many thanks. The problem did indeed turn out to be not having 100nF on the VBUS pin

View solution in original post

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4 Replies
Ekta
Moderator
Moderator

Hello @paroc_1316856 

> In case of PSoC 4L you do not require an external 22ohm resistor since the as the resistor is already integrated in the psoc device. You can refer to the image in the PSoC 4L Architecture TRM which shows this:

Ekta_0-1614876783118.png

I think the KBA mentions it because it is generic for PSoC 4L , PSoC 3 and PSoC 5LP devices.


KBA210620 also says that 0.1uF should be connected between VBUS and GND. Is this necessary even if VBUS is just used to sense the presence of the host, and enable the USB drivers?


In case you are using the VBUS monitoring feature of the USBFS component recommended to connect the VBUS through the resistive network, when the IO pin external to the Component option is selected. Main aim of such connection is to save pin from voltage picks on VBUS. An example schematic is shown in the following figure.

Ekta_1-1614877117085.png

Ekta_2-1614877316803.png

You can refer to the VBUS  Monitoring section of the USBFS component datasheet  to get more details about it.

I tried building the attached project, but I guess  a few files are missing like cmds.c, printf.c, PsocUSBExtensions.c . The USBFS configuration appears to be correct.

Best Regards

Ekta

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paroc_1316856
New Contributor II

Many thanks for your prompt reply.

Regarding the resistive divider and capacitor, do I need that even when using the VBUS Power Pad, P13:2?

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Ekta
Moderator
Moderator

Hi @paroc_1316856 ,

You wont require the resistive divider network, when you are using the VBUS Power pad P13.2.

You can have the refer to the CY8CKIT-046 schematic as a reference:

Ekta_0-1615369114023.png

Ekta_1-1615369176797.png

 

Best Regards

Ekta

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paroc_1316856
New Contributor II

Many thanks. The problem did indeed turn out to be not having 100nF on the VBUS pin

View solution in original post

0 Likes