General Questions Regarding Development Process

[Tae Choi]

I am evaluating the nRF52840 for developing wearable tech that would implement some basic sensors such as GPS & pedometer. Just have a couple questions regarding the transition from the development kit to the standalone SoC. After developing the application on the DK & using some UART sensors for prototyping, how would I go about running the application on an SoC in production? I'd imagine it wouldn't be possible to use the same sensors with the standalone SoC right? Also, how are the SoCs powered just by themselves without a DK?

[wpaul]

Your production application will basically be your own board design, which will include the sensors and anything else that you need (maybe a display?) and the Nordic nRF52840 System On Chip  (SoC). As the designer, its up to you to work out your physical board design, including power supply details. That means choosing a battery, designing a charger circuit, regulator circuit, and so forth. You can use the schematics for the nRF52840 DK board (which you can download from Nordic) as a guide for some of this.

Actually getting your firmware programmed into the nRF52840 chip in your production hardware is another design detail you'll need to work out. When you buy a bunch of chips for manufacturing, they're likely going to come with the internal flash blank, which means you're going to have to figure out some way to flash them. You're probably not going to include the same Segger J-Link debug hardware from the DK board in your final design. That leaves two choices:

1) Pre-flashing the nRF52840 chips before they're soldered onto your board. (They do make machines for this.)

2) Leaving an SWD header somewhere in your production board so that you can plug it into an off-board debugger and flash each board as it comes off the assembly line. (Note that the Segger J-Link hardware on the nRF52840 DK board can be used to debug and flash other devices.)

Option 1 is potentially more practical for large mass production runs.

Option 2 is sometimes achieved by just leaving some bare, unused solder pads on the board and construction a programming jig with matching pins. You just hold the jig and board together so that the pins and pads make contact.