Anthony Huy

Important changes to forums and questions

All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.

8 years, 9 months ago.

Is getNextTxMs() needed for 915Mhz?

In this example the code does:

(uint32_t)dot->getNextTxMs()

(a) Is this needed for US 915MHz? The mdot.h file says it always returns 0.

(b) What is the typical value returned?

Thanks

Question relating to:

Last updated: 12 Apr 2016
Connecting to gateway and sending packets with a MultiTech mDot. Lora, mdot, multitech

2 Answers

Mike Fiore
8 years, 9 months ago.

Anthony,

Like the documentation in mDot.h says, that function is only useful in the EU 868MHz frequency band. In the US 915MHz band, it always returns 0.

In the EU 868MHz frequency band, there are time on air restrictions that the mDot must obey to remain compliant. If the mDot is attempting to rapidly send multiple packets to the gateway, eventually all its available channels will be exhausted (because of the time on air restrictions) and the application will have to wait before it can transmit again. The getNextTxMs function shows how long the application will have to wait until there is a channel available.

Hope this helps.

-Mike

Thanks Mike. Related, how many channels can the conduit simultaneously handle and if the channels are exhausted, what do you recommend as a wait time before the mdot resends?

posted by Anthony Huy 05 Feb 2016

The conduit can listen on 8 frequencies at the same time.

If the mDot has no free channels, use getNextTxMs to see how long you need to wait before transmitting again.

posted by Mike Fiore 05 Feb 2016
Abhimanyu Dhone
7 years, 6 months ago.

Mike, Have you tried receive example for the EU868 Mhz? doe the time on air restriction affect the receive function of the mdot? Whats the best way to implement it?

Thanks, Abhi