The size of the event ringbuf was previously fixed to compile-time config
value, but it's necessary to sometimes increase this for applications that
have large characteristic buffers to read, or many events at once.
With this commit the size can be set via BLE.config(rxbuf=512), for
example. This also resizes the internal event data buffer which sets the
maximum size of incoming data passed to the event handler.
This allows the user to explicitly select the behaviour of the write to the
remote peripheral. This is needed for peripherals that have
characteristics with WRITE_NO_RESPONSE set (instead of normal WRITE). The
function's signature is now:
BLE.gattc_write(conn_handle, value_handle, data, mode=0)
mode=0 means write without response, while mode=1 means write with
response. The latter was the original behaviour so this commit is a change
in behaviour of this method, and one should specify 1 as the 4th argument
to get back the old behaviour.
In the future there could be more modes supported, such as long writes.
The address, adv payload and uuid fields of the event are pre-allocated by
modbluetooth, and reused in the IRQ handler. Simplify this and move all
storage into the `mp_obj_bluetooth_ble_t` instance.
This now allows users to hold on to a reference to these instances without
crashes, although they may be overwritten by future events. If they want
to hold onto the values longer term they need to copy them.
