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Hardware Errata

This page documents some issues with the hardware.

Rev 3

  • Footprint for RTC backup battery (BT301) is backwards
    • The + terminal of the battery connects to the GND node, and vice versa.
    • Resolution: Populate battery in reverse
  • RTC charger should be powered by system +3V3 rail
    • It's powered by the SoC's own 3V3 rail now, which toggles off during reboot
    • Use instead the system +3V3 rail
  • Incorrect power-on reset behavior
    • There is no reset pulse generated on boot-up (by an external reset generator… which we don't have. lol) which causes spurious boot failures
      • So, we should add a supervisor for the reset line
      • Generate a power on reset pulse of ~1 sec with the +5V rail
    • We may need to shorten the reset delay on the +3V3 voltage supervisor line
      • Alternatively – directly use the +3V3 input to switch it
    • This was caused by the RTC charger coming off the +3V3 SoM rail. Using the system +3V3 rail resolves this
  • Pulse shaper stuff
    • Adjusting it sucks as TP501 is on the analog side of the  filter, rather than the nice, pristine digital from U507
      • Fix: Add another test point at the output
      • Alternatively, we can probably work around this in software (with a special calibration UI?)
    • Possibly expand the adjustment headroom
  • Front panel connection
    • The pinout of the connector is mirrored (left to right) with respect to the front panel when assembled
    • We can probably leave this (using a longer flex to compensate) or fix it on either the front panel or controller board revision (probably the controller board)
  • Rear case fan (M501) connector sucks
    • The location is awful (it will be right underneath the analog board)
    • Relocate it elsewhere - but where?
      • Where VBUS LED is chilling
      • In the back by the expansion connector
        • We'd need to relocate some of the expansion IO stuff, like the termination and so forth
  • Power supply section sucks to assemble
    • Is there anything we can do to make this less awful
    • Also, add an easier way to power the board off DC
      • Spring/screw terminal near power supply area