Layout

There is an unlabelled (on the PCB silk-screen) 2-pin jumper (16) between the eMMC socket (14) and the SPI chip (17). It is designated as SW4 on the schematic diagram under "Board Information, Schematics and Certifications". The default condition is OPEN (no jumper). It is useful for controlling the boot as follows:

Default boot device (with no SPI software) is eMMC, then SDcard. If both the eMMC and the SDcard contain bootable images then the eMMC can be disabled by installing the jumper. This completely removes the eMMC from the resulting OS. If you wish the eMMC to be visible in the booted OS the jumper should be removed 2 seconds after applying power (and before the white LED comes on).

The possible combinations are summarised in the table below.

There is a second possibility to jumper your ROCKPro64: If you mess-up your SPI and are unable to boot, jumpering pins 23 (CLK) and 25 pin (GND) on the PI-2-bus header will disable the SPI as a boot device. (This was taken from the IRC logs, 09 August 2018 @ 17:23) You have to remove the jumper 2 seconds after having started your RP64 (before the white LED turns ON) otherwise the SPI will be missing and you won’t be able to flash it. Ayufan images contain (at the moment) only one script for the SPI and the RP64, it’s "rockpro64_reset_spi_flash". Other SPI scripts are dedicated to the R64 (as it is written on the name) and it will mess-up your RP64 SPI if you use them.