QTPy RP2040 USBBOOT net

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nirbec
 
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Joined: Mon Jan 23, 2023 6:58 am

QTPy RP2040 USBBOOT net

Post by nirbec »

Hi All,
Looking at the QTPy RP2040 schematic, i wonder why USBBOOT net is connected to GPIO21?
And also what is the diode D2 purpose? is it there to avoid sending 3.3V through GPIO21?

Attached is the schematic for your convenience.

Thank you,
Nir.
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adafruit_support_mike
 
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Re: QTPy RP2040 USBBOOT net

Post by adafruit_support_mike »

nirbec wrote: Thu May 18, 2023 5:12 am Looking at the QTPy RP2040 schematic, i wonder why USBBOOT net is connected to GPIO21?
The RP2040 bootloader uses USBBOOT as a pin selector. It the signal is low, the bootloader drops into USB Mass Storage mode so you can drop new firmware onto it. If the signal is high, the RP2040 boots the code you've uploaded.
nirbec wrote: Thu May 18, 2023 5:12 am And also what is the diode D2 purpose? is it there to avoid sending 3.3V through GPIO21?
The diode allows USBBOOT to pull the QSPI CS pin low (which is necessary to upload new firmware), but not to pull it high (which would disable the external Flash).

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