Commit 12f8569d authored by schneider's avatar schneider
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Update README.md

parent edf0bc62
......@@ -29,17 +29,22 @@ specifies them.
### I2C Port Expander Leakage
The PCAL6408ABS has its ADDR pin connected to VDDI2C. The datasheet specifies that it should be
connected to either VSS or VDDP. This results in an additional quiescent current of (max) 80 uA (see
page 27 of datasheet) while +3V3 is supplied to the Harmonic Board.
connected to either VSS or VDDP. According to the datasheet his results in an additional quiescent
current of (max) 80 uA (see page 27 of datasheet) while +3V3 is supplied to the Harmonic Board.
Actual measurements put it more in a region of 100 to 200 uA.
This effectively prevents putting the Harmonic Board into an ultra low power state while still
having access to all buttons. Only the power button which is routed to the PMIC is available in
this state (as +3V3 needs to be switched off).
### UART On USB-C
Diode D502 prevents proper UART communication with the debugger. It was replaced with a 0 Ohm resistor
during production.
### USB Core Supply
VDDB of the MAX32666 is turned on when USB power becomes available. This causes an additional current
draw by the CPU. This heats up the PCB and influences the temperature measurement of the
BME680 temperature sensor.
draw by the CPU. This heats up the PCB and influences the temperature/humidity measurement of the
BME680 temperature sensor. Making it switchable via firmware would make the card10 a better room climate sensor.
### 0201 Pad Geometry
During production there apparently were issues with the pad geometry of the 0201 devices. Maybe the
......@@ -74,10 +79,6 @@ This can impact debugging via SWD as there is no way to reset the MAX32666 while
D501, R507, R508 are not populated to achieve this.
### UART On USB-C
Diode D502 prevents proper UART communication with the debugger. It was replaced with a 0 Ohm resistor
during production.
### Display Connection
To save some space and allow the battery to be flush with the Harmonic Board, the display is soldered to
the top side of the Harmonic Board. This introduces a potential for large amounts of stress on the glass
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