I have been looking into programming for the nrf51822 and have a couple of the “low ram” 16KB versions of this chip on beacons and aliexpress development boards. I see that mbed os 6 has dropped the nrf51 series completely. Trying to compile for 5.15 bare-metal results in an error “Undefined symbol us_ticker_irq_handler”. Unfortunately, I can’t seem to find the right search terms to find the solution to this error.
Should I look elsewhere for a RTOS / bare metal development platform, or is it possible that this chip will have “custom target” support as a bare metal board going forward? Maybe there is a workaround for 5.15 bare-metal?
As far as I know, Nordic is still manufacturing this chip and it is still being used extensively in the BLE beacon industry. If this chip is essentially EOL and Mouser and DigiKey are late with this info, what should I look into as a relatively low cost, low power BLE capable alternative? nrf52?