thingSpeakWrite: too much zeros in decimal place

Cloud
1

Dear all,

I’ve browsed some topics related to save 3G data transportation. I found that reduce precision in decimal place may be one of methods. I used “round” to obtain one digit precision for some variables!

Here is the example:

temperature = round(temperature*10)/10;

However, the data strings still show many zeros in decimal place.

{"data":"{ \"1\": \"21.100000\",\"2\": \"-8.700000\",\"3\": \"45.000000\",\"4\": \"22.000000\",\"5\": \"985.000000\",\"6\": \"61.000000\",\"7\": \"0.000000\",\"8\": \"4.018300\",\"k\": \"4IPZ2DSN1X2A9EVO\" }","ttl":"60","published_at":"2016-09-12T15:59:38.745Z","coreid":"3500500009513433234561234","name":"thingSpeakWrite_All"}

Do I miss something here?

Thanks.

2

@changks, are you using sprintf() or String commands to create your json string?

3

I use the String command. Here is my code. Any comments? Thanks.

Particle.publish("thingSpeakWrite_All", "{ \"1\": \"" + String(Ta) + "\"," +
   "\"2\": \"" + String(Ts) + "\"," +
   "\"3\": \"" + String(Rh) + "\"," +
   "\"4\": \"" + String(VWC) + "\"," +
   "\"5\": \"" + String(Pa) + "\"," +
   "\"6\": \"" + String(Lx) + "\"," +
   "\"7\": \"" + String(UVindex) + "\"," +
   "\"8\": \"" + String(Vol) + "\"," +
   "\"k\": \"" + key + "\" }", 60, PRIVATE);
4

I’d always recommend snprintf() but you could also use String::format() and in both cases %.1f would be the format placeholder for one decimal place.

But I guess there might be an overload String(double, 1) to do the same thing (less elegant tho’).

3 Likes
5

Thanks a lot. It works great.