ble app uart communication between nrf52832 peripheral and nrf52840 Central

[vigneshms]

Dear community members

I have end nodes with nrf52832 (Soft device s132) that can communicate to a central nrf52832 DK in Connection mode based on ble app uart and multiple peripheral examples. The central DK board currently connects to a raspberry pi over uart for sending data to the Internet. I would like to know if I can replace the nrf52832 DK with a nrf52840 dongle to cut down cost and reduce size. I hope the soft device version on the dongle would be s140 - is it possible to establish multiple connections between a nrf52832 (S132) peripheral device and nrf52840(s140) Central device. Any help in this regard will be highly appreciated. 

Regards

Vignesh

[Edvin]

Hello,

The nRF52840 Dongle doesn't have regular IOs on the USB part, and it doesn't have a debugger on board. This means that it will not be able to get UART communication out of this port. 

If you intend to buy a lot of these, you can consider to invest in one nRF52840 DK to create an application that uses the USB port instead of UART to transmit the NUS messages. There is an example that does this located in SDK\examples\peripheral\usbd_ble_uart

It uses does basically the same as ble_app_uart, but uses the USB peripheral instead of UART. (the nRF52832 doesn't have a USB peripheral). 

Once your application for the nRF52840 is up and running, you can port it to the nRF52840 dongle.

The reason I recommend you to go with the nRF52840 DK first is that the dongle doesn't have an on board programmer, so it is a bit difficult to develop applications on the dongle itself, and since only the nRF52840 has the USB peripheral, I recommend you to use the nRF52840 DK to write your application.

Best regards,

Edvin

[awneil]

Edvin said:

The nRF52840 DK (sic) doesn't have ... a debugger on board.

You mean the Dongle doesn't have these.

vigneshms: The DK does have them - which is why it's the better option for developing (the clue is in the name!)

[vigneshms]

Hi edvin

Thanks for the quick response. As awneil had mentioned in the comment, I hope you mean that dongle doesn't have debugger and external IO lines. I'm totally fine with it as I need it to only operate as Central node with just uart enabled. Please let me know if I can program the dongle using the onboard debugger available on nrf52832-dk. 

I have no intentions to upgrade to nrf52840. I just want to know if I can run NUS service between nrf52840 dongle as Central  and nrf52832 device as peripheral. 

[awneil]

vigneshms said:

Please let me know if I can program the dongle using the onboard debugger available on nrf52832-dk.

Yes.

vigneshms said:

I just want to know if I can run NUS service between nrf52840 dongle as Central  and nrf52832 device as peripheral.

Yes, of course - the whole point of standards like BLE is that they are not locked to particular hardware.

[Edvin]

Yes and yes. Thank you, awneil. I meant to say the Dongle doesn't have the on board debugger. The DK does have it. (corrected in first reply). 

And as awneil also said, yes, you can use the debugger on the DK to program the Dongle. However, please note that you need to solder on a 10 pin debugging connector to the P1 output on the dongle. There are also some things you should consider if you erase the bootloader that is located on the dongle, which set the correct voltage level. I have not looked too much into the details, but there is a good blogpost about it here. Please read through it before you decide to erase what is already programmed on the dongle.

As mentioned, the dongle has a preprogrammed bootloader, so if you have an application which you want to use on the dongle, you can easily program it via the programmer app in nRF Connect for Desktop, but if something is wrong in the application, it is difficult to pinpoint without a debugger.