UplinkDwellTime not correctly applied on AU915

[gonzabrusco]

When the node receives the command TXParamSetupReq the network defines if the node has to limit the uplink and downlink time to 400ms (a.k.a. dwell time)

What you actually do in the current version of this library, is limit the datarate to 2 (0 and 1 do not comply with the dwell time limitation). But the function LDL_Region_convertRate does not take the dwell time into account when it should. The maximum payload allowable is dependent on the dwell time too.

[gonzabrusco]

This is where you apply the uplink dwell:

lora_device_lib/src/ldl_mac.c

Line 1726 in e017b22

self->tx.rate = LDL_Region_applyUplinkDwell(self->ctx.region, uplinkDwell(self->ctx.tx_param_setup), self->ctx.rate);

But you don't apply the uplink dwell limitation to the MTU:

lora_device_lib/src/ldl_mac.c

Line 1730 in e017b22

LDL_Region_convertRate(self->ctx.region, self->ctx.rate, &sf, &bw, &maxPayload);

What I did is add another parameter to LDL_Region_convertRate to tell the function if the dwell should be applied or not. If you are interested I can make a Pull Request for you to review.