Why can't I keep using S110/120 devices on nrf52840?

[Mitch996]

It appears that I must use S134 and S140 etc. Is it backward compatible? By that I mean I keep using S110/120 at the cost of not being able to utilize some of the latest feature?

[Wojtek]

S110/S120 is compiled for nRF51 devices - You just cannot use it on nRF52. BUT the api is not so different - just needs some small fixes to keep it working...

[Wojtek]

I have not worked with nRF52840 yet, but I assume its SD has similar API to newest nRF52832 API. I won't give you exact steps what lines you should change, but I can suggest you to just compile it with the api you were using before (i assume you want S110/S120 because you have used it before?). If something won't work, you will fix it. Also, you should read nrf51->nrf52 migration guide available somewhere on infocenter. You could just also take any nRF52 example available in SDK and build your app on top of it...