Currently I am developing a product based on microcontroller application. The product consists of 2 microcontrollers, the first one contains a GPL'ed binary code with some modifications, and the second microcontroller communicates with the first microcontroller using serial communication, and it sends it some commands to control it.
I have some questions:
I want the whole product to be sold without declaring the source code of the second microcontroller (the code should be proprietary).
Will it be enough to make it available to download the modified GPL'ed code of the first microcontroller?
I have read somewhere, that a proprietary software can use GPL'ed kernel of Linux, is my case similar to this? And if not, how can I make any workaround to comply with GPL license, and in the same time to keep the code of the second microcontroller to be proprietary?