WiFi 2.,4GHz range and performance

#1

Hi All,
Well done to the mBot team - fantastic tool for teaching any age.

Thought that I would start a new topic to discuss the performance of the 2.4GHz wireless serial link as supplied with the mBot kit.

The mBot works well with the USB serial link.

The mBot does not perform quite so well on the 2.4GHz link.

There seems to be two issues:

  1. Short range - within 1m the mBot responds as expected to commands/programs above this behaviour is erratic

  2. Communications robustness - the comms don’t seem to be protected by any error checking. Therefore incorrect values are written causing unintended behaviour.

The difficulty with (2) is that there is a large grey zone where the mBot responds incorrectly before the link finally drops and there is no more response.

Questions:
a) What devices are used in the 2.4GHz link?

b) What is the expected usable range of the link with 100% success?

c) What experiences have other users had?

Regards,
Graham

#2

+1
Want to know the same!

#3

Hi Graham,

A wireless link is always like this it is un-reliable if you don’t program something around it, I had the same with the WiFi dongle of Makeblock it uses UDP so it is not a reliable link. I updated my software with a protocol so it can reliable send and receive commands, and on the Mbot I made code that if it doesn’t get commands within a second it will stop what it is doing. By investigating the problem I found out that about 50% of the commands are not captured. I ended up with connecting a Rpi onto it works very nice, has also Wifi.

Groet,
Gert-Jan

#4

The 2.4G range I’m getting is really far. I have never seen an mBot lose range within a classroom setting. The 1m range issues you are experiencing sound odd.

Are your batteries fully charged in the mBot? That is the only case where I have seen range drop.

#5

Hi team,
Thanks for your feedback.

I have charged the batteries to ensure they are fresh and have run some tests.

I have also updated the IDE to 3.2.1 and reset the mBot firmware to default.

It is hard to say if this has improved the situation, with mBot response indicating commands are being missed even though the 2.4G link led is permanently on (2m distance). Below 1m the communications appears reliable.

I understand a little about network communications and agree that UDP is not reliable. However, a checksum byte could be added and your protection to force a halt would help harden the system. I would not have thought such a worthwhile addition would be too much effort to add.

I wonder if the keepers of mBot would like to comment?

Best regards to all,
Graham

#6