lpcware

VBUS assignment to ISP_1?

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by rjm on Wed Oct 28 04:45:31 MST 2015
The user manual UM10736 states in Table 91, that ISP_1 defaults to PIO1_11. That's clear from other parts of the documentation. However, USB_VBUS is declared as movable function, and the associated register defaults to 0xFF. But this should mean that USB_VBUS is not assigned by default to a pin at all. So, the init sequence should be responsible for this. Is that correct?

Another question: Why is it stated that VBUS should be assigned to the ISP_1 pin for ISP usability over USB?
A sample schematic (the LPCXpresso eval kit with LPC1549) shows that no Pull-Up is present on ISP_1. When I would not use a USB cable, the MCU would reset in an ISP-Boot-mode.

Hence I'm tempted to leave ISP_1 without any connection except a pull-up resistor (as is the case with ISP_0 in my own board, and then assign VBUS to another pin.

Please clarify these issues.

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