I am working on a project where I need to split incoming data from serial (time to be exact, so aa:bb:cc) and need to split it into aa then bb and cc, ideally into an array. I know I could use readStringUntil and make 3 separate variables, but I would prefer it is in arrays. Here is the code that supposed to do this. It works with predefined string (eg. 00:00:00), but with reading serial it says that the initializer fails to determine size of "input".Thank you in advance for helpful suggestions.
Here is the code:
void setup() { FastLED.addLeds<NEOPIXEL, DATA_PIN>(leds, NUM_LEDS); Serial.begin(9600); while(!Serial.available()){} //wait until Serial data received String vst = Serial.readString(); char buf[vst.length()+1]; vst.toCharArray(buf, vst.length()); char input[] = vst; char delic[] = ":"; char* sub = strtok(input, delic); while(sub != NULL){ Serial.println(ptr); sub = strtok(NULL, delic); }}
- Instead of
vst.toCharArray()(which copies the data) just directly usevst.c_str()which is a char array already. You don't needbufMajenko– Majenko2019-01-18 22:04:29 +00:00CommentedJan 18, 2019 at 22:04
1 Answer1
Your main problem is this:
char buf[vst.length()+1];You can't initialize an array with the return value of a function.
Instead you would need to usealloca to perform the same function:
char *buf = alloca(vst.length()+1);However, the way you're doing it is wasteful. You don't needbuf at all. You can directly access and manipulate the internalchar buffer inside the string usingvst.c_str();.
For convenience you can pointbuf at it:
char *buf = vst.c_str();To complete the picture here's a routine that takes the string and gives you three integers. Since we expect a specific format with only 3 sections to it we don't really need a loop.
// Use readStringUntil to avoid the 1 second delay.String vst = Serial.readStringUntil('\n');char *buf = vst.c_str();char *hourString = strtok(buf, ":");char *minuteString = strtok(NULL, ":");char *secondString = strtok(NULL, ":");if (secondString != NULL) { // Will only be true if we have two colons int hours = atoi(hourString); int minutes = atoi(minuteString); int seconds = atoi(secondString); Serial.print("It is "); Serial.print(minutes); Serial.print(" and "); Serial.print(seconds); Serial.print(" seconds past "); Serial.println(hours);} else { Serial.println("Invalid time format");}
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