nRF52833-DK uart communication with nRF52840-DK

RE: nRF52833-DK uart communication with nRF52840-DK

AngusKu — Wed, 07 Aug 2024 23:38:41 GMT

Noted.
Thanks everyone.

RE: nRF52833-DK uart communication with nRF52840-DK

Jared — Tue, 06 Aug 2024 17:50:24 GMT

Hi,

I'm not sure on exactly why, but this seems to be a side effect on the new boards that use the nRF5340 as the interface chip, versus older boards that used third-party IC for this. I think the solution is to use different GPIOs then the ones used by the interface chip.

regards

Jared

RE: nRF52833-DK uart communication with nRF52840-DK

hmolesworth — Thu, 01 Aug 2024 16:49:53 GMT

The 52833-DK doesn't use a hardware switch but a signal from the IMCU for IF_OFF so behaves differently to the 52840DK. Nordic engineers would need to provide further information on that, I don't have access to those details.

RE: nRF52833-DK uart communication with nRF52840-DK

AngusKu — Thu, 01 Aug 2024 08:01:39 GMT

I see but I am puzzled as to why the issue does not occur when I replace the receiver with the 52833-DK instead of the 52840-DK.

Could you explain why the 52833-DK does not have this issue?
Below is the hardware circuit for the 52833-DK regarding this part,
which seems to be the same as the 52840-DK?

RE: nRF52833-DK uart communication with nRF52840-DK

hmolesworth — Wed, 31 Jul 2024 14:57:16 GMT

The problem trying to use P0.05 and P0.06 on the nRF52840DK is that they are really not available as they are dedicated uart to IMCU and thence USB to PC. Yes SW6 isolates them, but then as you note the JLINK is also disabled.

You could cut SB52 and SB53 (actually just SB52) but then you would lose serial connection via USB to PC. A better solution is to simply use two other pins on the nRF52840DK for Tx and Rx as jared suggested

RE: nRF52833-DK uart communication with nRF52840-DK

AngusKu — Wed, 31 Jul 2024 03:57:34 GMT

Thanks for sharing this information.
Today, I tried to connect the usb cable to nRF52840 USB connector instead of IMCU USB connector, and the communication is normal. I didn't see the voltage being pull-up.

I have following quesitons, that I would like to ask you because I switch the SW6 from DEFAULT to nRF ONLY on nRF52840-DK, and the 52840 doesn't seem to boot up.
(when the application firmware runs, it should light up LED1, but I don't see LED1 turning on).

I tried connecting the USB cable from the IWCU USB connector to the nRF52840 USB connector,
but the situation remains the same.

1. If I switch SW6 from DEFAULT to RF ONLY for this issue,
Do I need to make any additional adjustments?

2. Additionaly, we still need to using JINK to debug and see the RTT conlose output,
Does the setting still work? or I have to use other GPIO pin ?
(To avoid issues arising from UART and the debug interface sharing the same pins

3. Is the reason why the 52833 does not have this issue because it does not use P0.06 and P0.08 for the debug interface?"

RE: nRF52833-DK uart communication with nRF52840-DK

hmolesworth — Tue, 30 Jul 2024 15:22:08 GMT

It is simple bus contention, maybe I wasn't clear: the nRF52840DK has an interface MCU (the debug interface) which is connected to P0.06 and P0.05. The IMCU is driving Tx at the same time the nRF52833 DK is driving Tx, both connected to the nRF52 Rx so when one drives high and the other drives low they fight and the voltage sits mid-rail or thereabouts.

SW6 on the nRF52840DK disconnects the unwanted IMCU Tx

RE: nRF52833-DK uart communication with nRF52840-DK

Jared — Tue, 30 Jul 2024 15:21:15 GMT

Hi,

Quick test to check if this is related to the new interface chip on the nRF52840 DKs is to repeat the test but with different GPIOs, can you change GPIOs from P0.06 and P0.08 and see if it's still an issue?

regards
Jared

RE: nRF52833-DK uart communication with nRF52840-DK

AngusKu — Tue, 30 Jul 2024 05:13:11 GMT

Released to use externally ??

When connecting two nRF52833-DK boards together via UART,
with one board sending and the other receiving, the signals are normal,
and the receiving board is able to receive UART data from the sending board
(without specifically switching SW6, keeping it at default).

My question is: Why does the logic-0 signal of UART get pulled up to approximately 1.6V when the receiving board is changed from nRF52833-DK to nRF52840-DK?

The following shows two nRF52833-DK boards connected together.
When measuring the UART RX signal on the receiving nRF52833-DK board, the logic-0 voltage is almost 0V, and communication works properly.

The following shows one nRF52833-DK and one nRF52840-DK boards connected together.
the logic-0 voltage is approximately 1.6V.

RE: nRF52833-DK uart communication with nRF52840-DK

AngusKu — Tue, 30 Jul 2024 04:46:09 GMT

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 ??

RE: nRF52833-DK uart communication with nRF52840-DK

hmolesworth — Mon, 29 Jul 2024 14:23:36 GMT

Tx and Rx are connected to the interface MCU (ATSAM) and need to be released to use externally. Try switch SW6, this switch controls this /IF_OFF interface selection.

RE: nRF52833-DK uart communication with nRF52840-DK

Jared — Mon, 29 Jul 2024 11:48:22 GMT

Hi,

Can you share a picture of the two boards?
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