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Android app - thingspeak - arduino
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June 22, 2019
3:55 pm
New Member
Forum Posts: 1
Member Since:
June 22, 2019
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Hi, i'm going to finish a project but i got stuck using an array sent from my Android app to Thingspeak (field 8) and then trying to get it from Arduino to assign data array to multiple variables.

So, from Android i send this URL :,5,30,100,30,150,60,215,245 and it correctly saves it.

Now from my compatible Arduino board ( Wemos D1) i collect data from field 8 in this way

String alarmsList = ThingSpeak.readStringField(myChannelNumber, alarmsFieldNumber, myReadAPIKey);

int alarmsList_len = alarmsList.length() + 1;

int Allarmi[alarmsList_len];

alarmsList.toCharArray(Allarmi, alarmsList_len);

var_allarme_1 = alarmsList[0];

but it doesn't work 🙁
Arduino IDE says:
Arduino:1.8.9 (Windows 10), Scheda:"WeMos D1 R1, 80 MHz, Flash, Disabled, 4M (1M SPIFFS), v2 Lower Memory, Disabled, None, Only Sketch, 115200"
Name.ino: In function 'void loop()':
Name_1.0:187:49: error: no matching function for call to 'String::toCharArray(int [(((sizetype)(((ssizetype)alarmsList_len) + -1)) + 1)], int&)'
alarmsList.toCharArray(Allarmi, alarmsList_len);
In file included from C:\Users\jasnandrea\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.0\cores\esp8266/Arduino.h:261:0,
from sketch
C:\Users\jasnandrea\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.0\cores\esp8266/WString.h:208:14: note: void String::toCharArray(char*, unsigned int, unsigned int) const
void toCharArray(char *buf, unsigned int bufsize, unsigned int index = 0) const {
C:\Users\jasnandrea\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.5.0\cores\esp8266/WString.h:208:14: note: no known conversion for argument 1 from 'int [(((sizetype)(((ssizetype)alarmsList_len) + -1)) + 1)]' to 'char*'
exit status 1
no matching function for call to 'String::toCharArray(int [(((sizetype)(((ssizetype)alarmsList_len) + -1)) + 1)], int

Does anyone have any advice for me?

June 24, 2019
9:32 am

Forum Posts: 885
Member Since:
March 7, 2017
sp_UserOfflineSmall Offline

You will probably have better luck on an Arduino forum or a C forum. The error is not with the ThingSpeak part, I think its with the datatypes for the variables in your toCharArray() call.

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