Some results !

A project log for Linux-ESPNOW

An attempt at implementing a direct link between a linux station and an ESP module using ESPNOW protocol for real time robot control

etienneEtienne 03/29/2019 at 10:130 Comments

All the results presented here have been obtained following this procedure (using the code mentioned in the previous Log) :

Effect of the data rate on round trip time and packet loss :

The figure 2 shows the round trip time and the number of packet loss depending on the data rate. Each point of the graph was obtained by averaging the values of 3 batches of 10,000 packets. These tests have been done both when the surrounding WiFi activity was 'very low' and 'normal'.

It seems that the data rate does not impact much the packet loss. A much more significant factor for the packet loss is the surrounding WiFi activity.

Moreover, as expected, the trend is that the higher is the data rate the shorter is the round trip. However, this relationship is not linear.

Further analysis on packet loss :

Since we choose to disable ACK to speed up the connection, we need to check that the packet loss is reasonable. However, the most important is that the loss is scattered. In fact, it would be very harmful in our robotic application to have big batches of packets being lost. It would mean that there is no feedback for 'long' periods of time.

The figure 4 shows that the size of the 'groups' of lost packets seems to follow a normal law centred on 0. The variance seems to be very low, so it is very rare (less than 0.1% in this example) to lose 3 or more packets in a row. Therefore the loss of packets is more acceptable.

Future improvements :

The next steps are :