Device Firmware Update (DFU) Over BLE and USB

Question

Hi, 
 What is the procedure and source code required to enable Device Firmware Update over BLE and USB. We are using nRF51822 chipset. Assume that our requirement will be like as follows, 
 
 Whenever the slave device connected to the master device (pc, smart phone..) either through BLE or USB, slave (nRF51822) should check for the firmware update, 
 
 2.If Firmware update is available, then the update should takes place. 
 Regards,
Balaji

Ole Morten · Accepted Answer

This is mostly something you'll have to find out yourself, depending on your requirements. However, SDK 4.4.1 includes an example of a BLE Bootloader, that can be used to upgrade the application running on an nRF51822 chip. Here is a discussion on how you can jump to this bootloader from your main application, for example when the Central device writes to a specific characteristic or similar. 
 I do think that it will be easier for the Central device to check for an update, and then tell the nRF51822, than the other way around. 
 Since there is no USB interface on the nRF51822, doing firmware upgrades will require a separate chip in addition. This could possibly be some kind of USB-to-UART chip, which could then use the UART bootloader to do the upgrade. Unfortunately, this isn't something I've tested, so I don't have much more information to give you on this.