No SPI clock pin on interstate 75w? Boot pin?

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1

I’m looking at the schematic for the Interstate 75W (rp2350) and it looks like the pins for the SPI bus are incomplete or unavailble?

GP16 and GP20 are available, as RX 0
GP17 and GP21 are available as CS 0
GP19 is available as TX 0

However, the SCK0 pins are all unavailable or are already used:
GP2 is used in the hub75 port
GP6 is used in the hub75 port
GP18 is directly tied to the RGB LED and is thus unavailable
GP22 is used by the BOOT pin
GP34 and GP38 don’t exist.

I’m trying to connect an SPI SD card module to the board, but if I connect something to the BOOT pin won’t it interfere with being able to flash or use the module properly?

Or does the fact that BOOT is active-low mean that just having the SD card touching it won’t cause a problem during the bootup process?

2

What about ADC0/NETLIGHT/SCK ?

3

Unless I’m horribly mistaken (which I fully accept as a possibility) that’s for the wrong SPI channel - it’s labelled as spi1 rather than spi0, and only one other pin for spi1 appears to be available.

I think I’m just going to have to move forward with trying the boot pin. I’ll measure that pin on the module with and without an SD card in it and see if the pin gets pulled down or not.

4

Ah, yes I do believe you are right. GP26 A0 is for SPI1 SCK.

5

This is a clock pin and the SD-card should not tinker with it - the clock is driven by the SPI host.

The boot-pin has a pull-up, but that should not matter since the SPI-device probably uses push-pull and will drive the clock low. BTW, in open-drain configurations you would even need a pull-up on the SPI clock.

So you have two things to check: will the SD-card work? And: will the boot-button still work as a boot button.

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6

I wired it up and use the BOOT pin for the clock, and it all seems to work fine, the SD card mounts properly, and the board boots up correctly.

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