This week I worked on assembling an additional 5 BLE stacks to bring the total to 9. To do this in an efficient way, I devised a method where the boards could be secured by the header pins into a breadboard to ensure they are aligned correctly after soldering. I also updated the KeyPeripheral code such that the keys will now go into a deep sleep mode after either 10 minutes without activity while connected to the central receiver or 1 minute without connecting to anything after being turned on. This reduces the battery consumption significantly, such that the keys can stay unplugged for multiple days and still be able to connect when pressed again to wake them up. However, I encountered an issue with the Arduino Nano 33 IOT, which is that it only seems to be able to connect to 7 peripherals simultaneously. There doesn’t seem to be a lot of documentation online specifically about this board and how to raise the limit, but there does appear to be some in place for the Arduino Nano 33 BLE. I have tinkered with some of the mbedOS files to increase the thread stack size and also some constants but the number of BLE devices that can be connected simultaneously remains hard capped at 7. Additionally, I have modified the receiver code so that it can identify and connect to new keys after the scan period is over. It does this by storing a copy of all the hardware IDs of each of the keys it’s connected to, and it then periodically attempts to connect to the new modules if it finds that they are available. The updated code can be found on bojuns/FP-Key-A_BLE (github.com)
My progress is on schedule this week.
Next week, I hope to unlock the connection cap to allow at least 8 boards to connect simultaneously to a single receiver. This way, it would be possible to connect all 16 switches simultaneously with only 2 receivers. If this does not end up working, then the next solution would be to make a two tiered design, where the switches connect to an intermediary receiver, which then forwards the signal to the central receiver.