Cannot tell when a host PC has connected to the nRF52832DK

RE: Cannot tell when a host PC has connected to the nRF52832DK

JONATHAN LL — Tue, 19 Aug 2025 12:06:56 GMT

Thanks for the feedback Ray!

RE: Cannot tell when a host PC has connected to the nRF52832DK

Raymond — Mon, 18 Aug 2025 23:39:15 GMT

Thank you for confirming these things. We hadn't had a strong enough pull up override the interface MCU's CTS pulldown. We're now using a stronger pullup and seeing the expected behavior.

However, just as feedback regarding this product, it's a real pain for us that the CTS line doesn't return to high-z to indicate when the USB-serial connection is closed. Without that behavior, there's no way for the application MCU to detect when it has a USB-serial connection established.

Perhaps this could be an improvement in coming versions of the interface MCU firmware!

Thanks again

-Ray

RE: Cannot tell when a host PC has connected to the nRF52832DK

JONATHAN LL — Wed, 13 Aug 2025 12:18:16 GMT

[quote user="raykamp"] The CTS signal is then "driven" (Assuming this means driven low) [/quote]

Correct, it uses an internal pullup.

[quote user="raykamp"]We aren't seeing that behavior. [/quote]

I have not tested this myself atm but I will look in to this.

[quote user="raykamp"]. I'll reach out to our FAE and sales rep in case that helps you/us get more support on this. [/quote]

Yes, always good to push form more than one angle if you need to get things done quick.

What SDK are you using, NCS verison ?

Regards,
Jonathan

RE: Cannot tell when a host PC has connected to the nRF52832DK

Raymond — Tue, 12 Aug 2025 19:05:04 GMT

JONATHAN LL , I'm working with RobHel on this. Per the Nordic documentation it sounds like this is the expected behavior:

- CTS is left high-Z by the interface MCU when no virtual-serial terminal is connected via a computer

- The computer software must connect and send a Data Terminal Ready (DTR) signal

- The CTS signal is then "driven" (Assuming this means driven low) "when the first data is sent or received" (TBD if this means a DTR signal from the computer or actual UART data coming through on the interface MCU's TX.

- Hardware flow control is continued to be used until a power-on reset or "until a new DTR signal is received and the detection is redone"

We aren't seeing that behavior. We're unable to make hardware modifications at this point unfortunately. We're using the DK within high-volume manufacturing equipment for testing a Nordic-based product. I'll reach out to our FAE and sales rep in case that helps you/us get more support on this.

Thank you

-Ray

https://docs.nordicsemi.com/bundle/ug_nrf52832_dk/page/UG/dk/vir_com_port.html

The UART signals are routed directly to the interface MCU. The UART pins connected to the interface MCU are tri-stated when no terminal is connected to the virtual serial port on the computer. The terminal software must send a Data Terminal Ready (DTR) signal to configure the UART interface MCU pins.

...

Automatic HWFC detection is done by driving Clear to Send (CTS) from the interface MCU and evaluating the state of Request to Send (RTS) when the first data is sent or received. If the state of RTS is high, it is assumed HWFC is not in use. If HWFC is not detected, pins P0.10/P0.21 P0.07 (CTS) and P0.05 (RTS) are free for the nRF application to use.

After a power-on reset of the interface MCU, all UART lines are tri-stated when no terminal is connected to the virtual serial port. If HWFC has been used and detected, P0.07 (CTS) is driven by the interface MCU until a power-on reset has been performed or until a new DTR signal is received and the detection is redone.

RE: Cannot tell when a host PC has connected to the nRF52832DK

Raymond — Tue, 12 Aug 2025 18:43:33 GMT

Here are the downloads for the interface FW:

www.nordicsemi.com/.../Download

RE: Cannot tell when a host PC has connected to the nRF52832DK

RobHel — Tue, 12 Aug 2025 15:41:08 GMT

Hey JONATHAN LL

Your understanding of what I'm trying to do is correct. I'm using whatever SDK comes with Zephyr 4.1.

I agree this would be simpler with the nRF52840, but we've built this test fixture with the 52832, and I'm surprised this is not possible.

The DK reference manual mentions that the mbed OB interface does not support HWFC through the virtual COM port. Do you know where I can find the .bin files needed to replace the interface firmware possibly with Segger J-Link OB?

Thanks,

Rob

RE: Cannot tell when a host PC has connected to the nRF52832DK

JONATHAN LL — Tue, 12 Aug 2025 12:31:10 GMT

Just to make sure that I understand you task correctly,

You want to make the nRF52832 register if there has been a connection or disconnection of the USB on the DK.

What SDK are you using?

There is no easy way for the nRF52832 to know if something is connected to the USB as it itself does not have it, but it uses the onboard interface MCU to communicate converting UART to USB.

Using the nRF52840 or 833 that has USB built inn you could use USB CDC to detect this i belive. Might be more in line with what you want to do.

RTS should be asserted or deasserted depending on the state of the connection to see if there is any action so this should indicate that something is ready to listen, but it does not guarantee that the comport is opened\closed i belive.
CTS could maybe be used to check if USB is connected or not, but an alterative is to connect a GPIO to the VBUS here so you will see a signal here, but you will need to step down the voltage, can use a voltage divider to test.

You will need to implement something in SW here to get it working as I dont think there are any examples available here.

Regards,
Jonathan

RE: Cannot tell when a host PC has connected to the nRF52832DK

RobHel — Wed, 06 Aug 2025 17:53:55 GMT