CYBT-343026-01 PUART RX on PIN14

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VM
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We are trying to use a custom-built firmware on the above module.

The module is connected to an LPC1767 MCU using PIN 14 (GPIO_4,PUART_TX/P31) and PIN 15 (P4/P24 PUART_RX/P4). We have our own custom hardware.

We initialize the UART at startup (application init):

    wiced_hal_puart_init();

    wiced_hal_puart_select_uart_pads(WICED_P04,WICED_P31, 0, 0);

    wiced_hal_puart_flow_off( );  // call wiced_hal_puart_flow_on(); to turn on flow control

    wiced_hal_puart_register_interrupt(APP_puart_rx_interrupt_callback);

    wiced_hal_puart_enable_tx( );
    wiced_hal_puart_enable_rx( );
When the BT module transmits we have a good signal (yellow one in the image named device.jpg) and the MCU is able to receive data.
When we transmit from the MCU we have a ~1V offset that prevents data reception from the module (purple signal).
We tested on the EVB (600-20109-01) and we see the same issue, but with a smaller offset (due to the different driver on the host side, here we have the USB-2-UART chip and not our MCU) that allows the module to correctly read the data (EVB.jpg, offset is smaller but still noticeable).
We flashed the ez-serial firmware on the EVB and on our device and there the signal correctly drops to 0V on both the actual hardware and the EVB (see EzSerial.jpg).
This makes me suppose that there is something wrong in the way P4/P24 is configured by the wiced_hal_puart_select_uart_pads function. I tried to configure both pins (P4 and P24) with the GPIO library, clearing any pull-up/down and setting P24 as input (to prevent interference), but this doesn't seem to work.
I see no pin mixing functions in the wiced SDK libraries we are using and I couldn't find any specific documentation about the SOC itself (the CY20706 DS mentions the G8 pad and its multiple functions but does not provide information about how to configure it...).
Is it possible to configure the P4 pin in the same way ez-serial does to ensure good signal quality and interoperability with the different MCUs we plan to use in our designs?
Unfortunately, we can't use ez-serial since it does not provide all the features we need.
 
 
 
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VM
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Ok, here you can find the solution:
https://community.infineon.com/t5/Studio-Bluetooth/Could-I-config-WICED-P04-as-GPIO-with-CYW20706/td...
It would be nice to see those "secret" registers documented somewhere in the DS...

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VM
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I downloaded the latest version of modus toolbox (we are currently using an old SDK), built and downloaded the PUART sample and I see the same behavior. The quality of the TX (host to module) signal is the same as it is with my current code. 

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VM
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I see the issue happening with both release and debug builds of the application.

Even if I configure the pin as a GPIO input:
wiced_hal_gpio_configure_pin(WICED_P04, GPIO_INPUT_ENABLE, 0);

I see that the TX signal does not return to 0V (TX.PNG, see TX-RX.png to compare it with a correct signal, from module to host).
In theCYBT-343026-01  datasheet I see that the P4/P24 pin is on "silicon-pi" G8 that is shared between P4/P24 and BT_CLK_REQ.

I see that configuring P24 also as input or leaving it configured does not change the behavior.
So I suspect that BT_CLK_REQ is someway involved... but I could not find any SDK function to act on that signal.

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VM
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5 replies posted 5 sign-ins First like given

Ok, here you can find the solution:
https://community.infineon.com/t5/Studio-Bluetooth/Could-I-config-WICED-P04-as-GPIO-with-CYW20706/td...
It would be nice to see those "secret" registers documented somewhere in the DS...

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AnjanaM_61
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5 comments on KBA First comment on KBA 5 questions asked

Hello @VM 

Glad to know that you got the resolution from previous threads.

We will try to add this workaround in any of our documents. Unfortunately the register details are not exposed. Sorry for the inconvenience caused. 

Regards,
Anjana

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