[Little Brosers] The End is Near

Here I am, writing my last post in the logbook. Time passed quickly and right now we’re working around the clock to finish the project before Friday.

As far as I’m concerned, the certificate verification problem that I was stuck on 2 weeks ago was solved a long time ago. The authentication process on the drops is working like a charm, with the drop disconnecting if there is a problem with the user certificate or the challenge response.

On the Android side, I implemented the filters based on the networks we’re active in. Then the results are analysed to tell if we should connect to a drop or not. In addition to that, I have laid out the entire connection process on drop discovery, with stubs for the yet unwritten processes. I’m currently working on finishing the authentication process on the Android side. Challenging a drop and verifying its response, as well as responding to its challenge are working perfectly well. However, given that the user certificate is not yet ready, I’m putting that part on hold for now, and working on communicating with the server to obtain the user certificate on signup.

During last week, while implementing the authentication on Android, I realized that we couldn’t write more than 20 bytes (the default MTU size on the drop) to a characteristic, which was problematic given that we have much larger characteristics, like the challenge/response and the certificate. I solved this problem by increasing the MTU size on the drop to 214 and implementing long write operations, which allow Android to break the data into multiple packets that are sent sequentially to the drop. Upon reception the drop’s BLE stack asks for a memory block that will hold the temporary data, and then writes the whole data in the characteristic.

I hope you enjoyed reading my blog posts as much as  I enjoyed writing them, but now, I have to get back to work.

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