CY8CKIT-043 UART deep sleep problem

[user_2726841]

Hello all,

I'm currently trying to implement the deep sleep mode into the CY8CKIT-043 in my own project.

My problem is that the current won't sink while the UART-SCB module is enabled in the schematic.
I expect a current around 1..5µA when nothing is connected to the KIT instead it sinks between 1mA
and 2.5mA. By de-selecting module by module I've reached the point that the root cause is the UART module.
To ensure if it's the TX-Pin or the RX-Pin I've changed the configuration of the module and retried it.
With TX-Only it's like expected with RX-Only it draws to much.

To be sure that I didn't do anything wrong I have copied the complete project from:

https://iotexpert.com/2017/12/14/psoc-4200m-low-power-with-wdts/

And again it's the same behaviour...

I've changed the SWD mode already to GPIO and tried with a 3.3V instead of 5V without
any success.

Is there a hardware related bug on the KIT or in the MCU?

[user_2726841]

Ihave changed the drive mode from the RX-Pin from "high-digital input" into "high-analog input".

The result is:
RX-Pin as "digital input" ~ 1.4mA
RX-Pin as "analog input" ~ 0.8µA

If there's a chance of using the RX pin as a digital "wake-up" pin it would be very helpful,
otherwise I have to use the low power comparator where an analog pin is routed to the RX-pin.

[NoriTan · Accepted solution]

It seems that the RX-Pin is in intermediate potential and the input buffer draws flow-through current.  Please touch to the RX-Pin with your finger. The current consumption will be randomly changed.  The internal input buffer is disabled in the "analog input" mode to stop the flow-through current.

If you changed the drive mode of the RX-Pin to "Resistive pull up" mode, the RX-Pin potential will be fixed as HIGH and the flow-through currents stops.

If possible it is also effective to put a pull-up resistor to the RX-Pin.

Regards,

Noriaki

[user_2726841]

Thank you very much,

I've connected a 3.6k Ohm resistor between RX-Pin and VDD.
The current dropped from 1.4mA to 0.8µA.

Regards,
Eduard