Figure out the frequency of the publishing

[tarek20501]

Experiment with Cellular.getDataUsage() to figure out the frequency of publishing such that we do not exceed 3MB/month

[ShreyansK2000]

Using the Cellular.resetUsage() method to set all internal counters to 0 at every power cycle, we were able to test for the size of packets sent and received for every publish with the use of webhooks. The test conducted published 2 times each, with 10 cycles of the sampling in between them to allow for stabilization of the values. For now, we conducted 10 trials.

Trial 1, 7

	TX	RX	Data(i)TX - Data(i-1)TX	Data(i)RX - Data(i-1)RX
Data(0)	287	287
Data(1)	394	348	107	61
Data(2)	501	409	107	61

Trial 2-6, 8-10

	TX	RX	Data(i)TX - Data(i-1)TX	Data(i)RX - Data(i-1)RX
Data(0)	598	414
Data(1)	705	475	107	61
Data(2)	812	536	107	61

In all cases, regardless of the initial data consumed for the handshake, the total data exchanged for a publish event is 107 + 61 = 168 bytes. We can leverage this to calculate the frequency of publish events

[tarek20501]

Next week let's try getting data usage at the beginning of the setup and reset. See if you get consistent data usage for the cloud handshake

[tarek20501]

Let Data(n) be the function that returns data usage at nth Publish call where n = 0 represent data usage resulted from the initial handshake with the Particle Cloud. The following is the algorithm that calculate publishing period:

Data(2) - Data(1) = MessageSize

(MonthlyDataLimit - Data(0)) / MessageSize = NumberOfMessages/Month

NumberOfMessages/Month * Month/31 = NumberOfMessages/Day

NumberOfMessages/Day * Day/24 = NumberOfMessages/hour

NumberOfMessages/hour * hour/(60*60) = NumberOfMessages/second

second/NumberOfMessages = PeriodOfPublishing (seconds)

[ShreyansK2000]

I conducted a few trials this week to see how many bytes are sent and received over the initial handshake. The following are the results:

Trial	TX	RX	Data(0)
1	3109	2365	5474
2	3111	2361	5472
3	3111	2365	5476
4	3109	2363	5472
5	3109	2363	5472
6	3111	2361	5472
7	2704	1783	4487
8	3111	2363	5474
9	3111	2365	5476
10	3511	2486	5997
11	3107	2361	5468
12	3109	2365	5474
13	3111	2365	5476
14	3111	2365	5476
15	3107	2365	5472

Given the larger than normal TX and RX values in trial 10, I think we should consider something around 6200 bytes or higher as the handshake establishment bytes in our calculation for total bytes used.

[tarek20501]

Thanks for your dedication @ShreyansK2000 Next time we meet up will turn the algorithm into code. Just one question... can you tell me where you put resetUsage and getUsage calls for your last experiment?

[ShreyansK2000]

getUsage at the start of setup(), then for 10 calls of loop(), I let the numbers stabilize, and then call resetUsage. I also let that run for at least 10 loops each time just in case, after reset TX and RX values always stayed at 0.