nRF52833-DK uart communication with nRF52840-DK

[AngusKu]

Hi,

I use two nRF52833-DK boards for uart communication (both using pin p0.06 for TX and p0.08 for RX),
with their TX and RX and GND pins connected to each other, and perform a UART transmission test:

One board is responsible for sending UART data, and the other board is responsible for receiving the data, the transmission works without any issues.

However, when I replace the receiving nRF52833-DK board with an nRF52840-DK board,
I find that when the UART RX pin on the nRF52840-DK receives UART data from the nRF52833-DK and the data is bit1,
the voltage level is about 3V, which is similar to the nRF52833-DK.
But when the data is bit0, the voltage level is raised to around 1.6V and cannot drop close to 0V, causing transmission problems.

Does the nRF52840-DK require any additional configuration to work with UART communication from the nRF52833-DK?
All DK boards are powered by VDD.

[Jared]

Hi,

1. Can you share a picture of the two boards?
2. If you disconnect the nRF52833 from the nRF52840 and just measure on the TX signal from the nRF52833, does the signal go all the way down to 0v for a logical 0?

regards

Jared 

[AngusKu]

1. 


2.
 yes,
 If I disconnect the nRF52833 from the nRF52840, the signal go all the way down to almost 0v for a logical 0.


Btw,
I programed the smp serve example code on the receive end.
I implemented the smp client on the transmit end.
Two nRF52833-DK work as expected and I don't have any other hardware setup.
If I replaced the receive end from nRF52833 to nRF52840, I encountered the uart voltage level issue.

I want to know if any special hardware settings are required for UART communication between an nRF52840-DK and an nRF52833-DK ??