January 24, 2021

EBAZ4205 Bitcoin miner board - LEDs, buttons, reset

The red and green LEDs on the board edge are connected to W13 and W14 according to the schematic. These are IO_LXXY pins and are not directly accessible from the ARM (PS) side of the chip.
So there is no way to manipulate the LED's without learning to deal with the FPGA (PL) side of the chip.

Buttons

There are two buttons (S2 and S3). My board only has a button mounted on S2. These are connected to U3.A17 and U3.A14 according to the schematic. These are connected to MIO pins and can indeed be accessed directly via GPIO from the ARM side. I wrote some bare-metal code to read the GPIO connected to this button.

#define MIO_S2_BUTTON	20
#define MIO_S3_BUTTON	32
  • Github - my bare metal button monitoring code.

    Reading button status from linux

    I received an email from a kind soul on 1-24-2021 who reported the following:
    I extracted "/opt/work0/btc_upgrade.tar.gz" and found a "reset_button" script. Within is a reference to "/sys/class/gpio/gpio926/value". I was able to quickly confirm that cat'ing this pseudo-file would reflect '1' when the S2 button was pressed.
    The S2 button is MIO 20 and the S3 button is MIO 32. For whatever reason, the MIO bits get started at "906", so MIO-20 becomes gpio926 and MIO-32 will be gpio938.

    Reset

    Reset has no button. It is handled by an SGM706-SYS8 chip, which is described as a "microprocessor supervisor circuit". A 35 page datasheet is available, and this thing is shown on the schematic.

    Very likely a button could be wired to this thing. What I have done instead is to wire up a button to the 12 volt supply so that the button momentarily interrupts power which gives the same effect as a reset button, albeit not quite so gently.


    Feedback? Questions? Drop me a line!

    Tom's Computer Info / tom@mmto.org