ESP8266 Community Forum

- Sat Sep 13, 2014 12:58 pm #523 If you want BT coexistence, make the BT SOC the main CPU and turn this one into a peripheral. Chips like the nRF51 have plenty of pins to work with. I am also 100% sure there is demand for a design that combines this chip with a BLE SOC. At least a dozen different people have asked me about it. These BLE SOCs have many more peripherals.

Also, there are multiple BT coexistence schemes which need different amounts of pins.

An interesting application would be to leave the BLE chip on all of the time on batteries. Then power on the ESP8266 only when needed for wifi access. It is possible for a normal wifi router to create a noise pattern that a BLE radio can receive. That noise pattern can signal the BLE radio to power-on the wifi one.

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- Sat Sep 13, 2014 1:17 pm #526 Yes, you are right: unless you require simultaneous WiFi/BT operation, the best option is to have BLE turned on, an turn on WiFi only when required, given that it consumes ~x40 the power of BLE.

I didn't know about his noise pattern thing: I know that a WiFi channel takes 20 BT ones, but how can you make sure you are using the right channels? Or do you spread over the whole band?

- Sat Sep 13, 2014 1:50 pm #528 Bluetooth does not frequency hop except when it is in a session. When not in a session it monitors three advertising channels.

I'll poke around in Google. A couple years ago there were several papers written on doing this.

Here's one paper:
http://www.cs.iastate.edu/~wzhang/papers/MASS12-Qin.pdf

But there is another one where the wifi router was used to generate noise on the advertising channels. It works at something like 100b/s but that is plenty to tell the BLE chip to turn on the wifi one.

Maybe it was this one:
http://arxiv.org/pdf/1209.6186.pdf

Yes, I think it was that second paper. It uses the CCA hardware (clear channel assessment). Then it generates interference of varying lengths of time. Those varying lengths can encode simple messages - like wake up.

Where I get my modules