Posted on May 12, 2014 at 16:07The System Loader really isn't going to help you in this situation. You will need to implement your own boot loader, or in-application update. There are several IAP examples for STM32 parts, using USART, Ethernet, etc, as indicated earlier you should review these to get a sense of things.
Ideally you want to download and stage the firmware somewhere, like an SD Card, or other memory. You can go directly to FLASH, but writing to it will stall execution of the processor if it is running any other code from FLASH. This can be addressed by running code from RAM, but this makes things more complicated, especially if you have little experience in this space.
Using GSM/CDMA modems I've use HTTP to download firmware updates, you need good flow control on the modem/serial to do this, as the stalling of the CPU will otherwise cause over/under runs on the USART. For serial updates from a terminal, things like XMODEM work very well as they have inherent flow control and pacing.
HTTP GET is a fairly simple TCP/IP based protocol, I know others who have used FTP, it depends a lot of your familiarity with the protocols, methods, and sockets. If you have little, or no familiarity, I would suggest experimenting with socket programming on a PC before trying to migrate to embedded and modem based solutions.
