Suggestion: Nordic MCU without the radio

[ecorm]

This is not a support request, but merely a suggestion to the company. I need a host MCU for my project which will use an nRF52-based pre-approved module. I would like to use a second nRF52 as host MCU with the radio disabled for the following reasons:

• Can use same VS Code toolchain for both the module and host MCU
• Familiarity with nRF52 product family can be applied to both module and host MCU development
• Can re-use the same code for serial communications between module and host MCU

I was considering the nRF52832 for my host MCU, but it is severely lacking in UART peripherals: it only has one!

A Cortex-M4F MCU from a competitor that costs about the same has way more peripherals available for the same pin count. This is not surprising, as this competing product does not include a radio taking up silicon real estate.

So I'm thinking: wouldn't it be nice if Nordic had a Cortex-based MCU without the radio?

[Turbo J]

UART is not a good choice for the MCU-to-MCU communication since its slow and you cannot really shut down the HF clock unless you use more pins.

I recommend using SPI (SPIS+SPIM) instead.

There are NRF52x and NRF53X chips with >1 UART(E) available.

Note that its usually cheaper to use a bigger MCU like NRF53x instead of 2 smaller ones.

[ecorm]

Turbo J said:

UART is not a good choice for the MCU-to-MCU communication since its slow and you cannot really shut down the HF clock unless you use more pins.

MCU-to-MCU speed is not a problem for my application, but being able to shut down the HF clock is not something I had considered. Thanks for the suggestion.

I still need a UART to communicate with an external device, plus I would like to have a spare dedicated UART for debugging purposes.

Turbo J said:

There are NRF52x and NRF53X chips with >1 UART(E) available.

I'm now looking at the nRF52833 as a possibility, but the easier-to-solder QFN40 variant doesn't have enough spare GPIOs. The QFN48 variant of the nRF52840 doesn't have the USB device peripheral that I also need. I'm considering the use of I2C I/O expanders, which may help in PCB routing.

Turbo J said:

Note that its usually cheaper to use a bigger MCU like NRF53x instead of 2 smaller ones.

If it were purely just BOM costs, then yes I would agree with you. But I need to use a pre-approved RF module to reduce certification risk/cost, and such a module won't provide me with enough I/O to implement my application.

I'm not stuck; I can go with a competitor's MCU for the host MCU. It's just it would have been nice to the use same toolchains for both MCUs.

[ecorm]

Just a placeholder answer so that I can close this ticket.

[ecorm]

One advantage of using UART for the MCU-to-MCU communication is that it's easier to test the slave MCU using a PC. In my case, I don't need high throughput. My application is a kind of "smart" remote control.

[ovrebekk]

Hi

Nordic is a relatively small company, and our focus is on low power wireless products. You are not the first to ask for MCU only products, but there are no current plans to support this. Even if we were to simply remove the radio from all the existing nRF52 parts and release MCU only parts this would be a huge undertaking from our side, and it would be hard for us to compete with companies that have a huge catalog of MCU's already. 

Either way, good to see that you got some alternative suggestions to your problem and have decided to close the ticket

Best regards
Torbjørn