Delay or lag in sending messages at a rate of 30ms or lower

[programmeddeath1]

I am using the olimex esp32-evb-ind to execute the position,velocity and acceleration of a robotic arm. The path is generated on a cpu and the coordinates are then sent to the esp32 over ethernet cable.

When sending data over a control cycle of 0.04 (1 point generated every 0.04s or 40ms). The communication time from the cpu to esp32 is avg around 4ms (RTT) ie 2ms for communication
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ID	sentTime	ReceiveTime	ExecutedTime	Communication time	Execution time
1	1720436672	1720436672	1720436672	4.03	4.96
2	1720436673	1720436673	1720436673	3.72	4.54
3	1720436673	1720436673	1720436673	4.01	4.96
4	1720436673	1720436673	1720436673	3.5	4.37
5	1720436673	1720436673	1720436673	4.19	5.49
6	1720436673	1720436673	1720436673	3.24	4.32
7	1720436673	1720436673	1720436673	3.62	4.5
8	1720436673	1720436673	1720436673	3.87	4.64
9	1720436674	1720436674	1720436674	4.27	5.19
10	1720436674	1720436674	1720436674	4.27	5.17

But if i reducee the control cycle to below 0.03, eg at 0.01, there seems to be significant lag and pile-up of messages causing constant lag
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Test 1	sentTime	ReceiveTime	ExecutedTime	Communication time	Execution time
1	1719317147	1719317147	1719317147	6.15	14.68
2	1719317147	1719317147	1719317147	14.63	25.86
3	1719317147	1719317147	1719317147	25.57	26.35
4	1719317147	1719317147	1719317147	25.49	26.54
5	1719317147	1719317147	1719317147	26.25	27.66
6	1719317147	1719317147	1719317147	25.65	26.82
7	1719317147	1719317147	1719317147	25.97	27.35
8	1719317147	1719317147	1719317147	25.17	26.31
9	1719317147	1719317147	1719317147	24.14	25.3
10	1719317147	1719317147	1719317147	24.15	25.05

I tried controlling the background processes by creating the mqtt callback task to pin to a core using xTaskCreatePinnedToCore. Such that it was run on core 0 as well as core 1, but the lag seems to remain.

Also the lag seems to be more on control cycle of 0.02 and 0.03 - <style type="text/css"></style>

1	1720436867	1720436867	1720436867	3.12	28.74
2	1720436867	1720436867	1720436867	28.88	55.37
3	1720436867	1720436867	1720436867	55.61	56.43
4	1720436867	1720436867	1720436867	55.33	56.06
5	1720436867	1720436867	1720436867	52.8	53.77
6	1720436867	1720436867	1720436867	47.12	48
7	1720436867	1720436867	1720436867	47.66	48.47
8	1720436867	1720436867	1720436867	47.18	47.99
9	1720436867	1720436867	1720436867	47.01	47.81
10	1720436867	1720436867	1720436867	47.2	48.27

I tried changing the message data size, sending in json format or as encoded byte format, but there seems to be almost no difference in the processing time.

Is this a limitation with the cpu processing capabilities of the esp32 that its not able to process points at such high frequencies.

The esp32 DOIT kit which runs WROOM-32 is able to achieve faster times with uart at a baud rate of 4000000. It seems counterintuitive that uart is faster here than ethernet or mqtt over LAN.

I have connected the esp32 over a link-local only lan setup and no router, the ping times are around 0.3ms.