psoc4 powered by UART?

[GuNo_288966]

Hi,

   

I am using a CY8CKIT-049-42xx, powered by a MINIPROG-3 at 3.3V.

   

I have an UART with TX and RX that is connected to a Raspberry Pi (3.3V). TX is on P1.5, RX is on P1.4.

   

As soon as I connect the RX and TX lines (and 0V) to the Raspberry, the PSoC gets powered over these lines, even if the MINIPROG is not connected. I have not yet checked if the firmware is really up and running, at least both LEDs on the CY8CKIT are on.

   

When I connect the MINIPROG-3 and start debugging, the program runs fine until a character is received from the PSOC. In this case the debugger steps into UART_1_GetRxBufferSize() and never returns. It is not possible to halt the software, only stop debugging works.

   

The UART is configured with 16 bytes receive buffer and 16 bytes send buffer, interrupts are enabled.

   

Two questions:

   

How can I avoid the PSoC to be powered over the UART connection?

   

Why does the firmware get stuck in UART_1_GetRxBufferSize()?

   

Any ideas are welcome.

[rola_264706]

        Post your code so we can check your code.   

[Bob_Marlowe]

Powering the prototype kit using UART will not work, there is no internal connection. Connecting RX and TX without powering the board may destroy your PSoC. Did you remove the snap-off programming part?

       

Bob

[GuNo_288966]

Hi Bob, the snap-off part is still there.

   

I now put a 10 kohms resistor into the RX line (RX of the PSoC) to prevent energy to come over this path. Now it works as intended. The PSoC does no longer power up when RX is connected.

[EmHo_296241 · Accepted solution]

Hi,

The problem might be your PSoC getting back powered. The GPIO pins have ESD protection diodes which is causing the backpowering issue. You may use the SIO pins with hot swap option.