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[ZeROSEro7] BLE fully operationnal

I made the last improvements to the BLE control and enabled fast two-way connection to a characteristic with a simple programming interface. I am using Write requests with no response on the GATT client side and notifications on the server side along with the highest MTU available for the nRF52 (200+ bytes). This will be usefull for the USB sniffer where we will download a great amount of data.

I ran a test program on our SpyTalk custom PCB and the BLE and LoRa chip worked. Yet, because of difficulties when welding, one of the Quartzs doesn’t seem to work but it is not critical. It will only raise consumption during off time.

I prepared a test program on the nRF SPI for the USB Sniffer that sends packets to the STM32 and expects a response. This program is proven to work because it did with the LoRa chip so now Erwan and I can implement the SPI driver on the STM side and imagine a simple protocol to exchange our data. This part will be even easier on the Stealth Drop because only a wakeup is sent. It could be done with a simple GPIO.

My next priorities are to finish the USB Sniffer, including the final user interface, and to design and implement a simple protocol over LoRa for the SpyTalk. This protocol will include at least addressing, retransmission, and basic AES encryption. I abandonned using LoRaMAC because this protocol, despite being very efficient for what we want to achieve, requires gateway stations which are usually public and it is not what we planned as our network architecture. It would also require different hardware. Given the time left, I may also add synchronization for lower RX time, better security with changing keys and any other ideas that may come to my mind. I’d also like to add bonding and security on the BLE connections.

Erwan and Vincent made great progress on their side and I think we are very close to having every of our 3 gadgets fully working!

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