Trouble Comparing Bluetooth-Sent ASCII char in iOS - ios

Question

I have an iOS application that talks to a RedBearLab Arduino device. My code that I use to send an int via bluetooth from Arduino to iOS is as follows:
void sendMyInt(int myInt) {
char b[4];
String str;
str=String(myInt);
str.toCharArray(b,4);
for (int i; i < 3; i++) {
char toPrint = b[i];
ble_write(toPrint);
}
}
Here is my code on the receiving end:
-(void) bleDidReceiveData:(unsigned char *)data length:(int)length
{
NSData *d = [NSData dataWithBytes:data length:length];
NSLog([NSString stringWithFormat:#"%#",d]);
NSString *s = [[NSString alloc] initWithData:d encoding:NSUTF8StringEncoding];
const char* clearChar = "!";
if ([self.label.text isEqualToString:#"Label"]) {
self.label.text = #"";
}
else if ([s isEqualToString:[NSString stringWithUTF8String:clearChar]]) {
self.label.text = #"";
}
else {
NSString *store = self.label.text;
NSString *full = [NSString stringWithFormat:#"%#%#",store,s];
self.label.text = full;
}
}
The final else statement fires somewhat as expected, and a value of 233! is printed out to the label over and over again, getting longer each time eventually forming things like 233!233!233! etc. As you can see, I am using a character (!) sent over a function to clear the label, but it never clears. The integer is the ASCII code for the exclamation point:
void clearLabel() {
int clearString = 33;
char excalamtion = clearString;
ble_write(excalamtion);
}
Why would this not clear the label? I assume it has something to do with the clashing formats, but I'm not really too good at that even after reading some documentation. For the else if statement I also tried this
if ([s isEqualToString:#"!"])
but that didn't work out either... Any help would be appreciated.
EDIT:
I forgot to put in my loop code so you can see function calls. Here it is:
void loop()
{
if ( ble_connected() ) {
int a = 223;
sendMyInt(a);
delay(1000);
clearLabel();
delay(1000);
}
ble_do_events();
}
EDIT 2:
Based on a suggestion by #Duncan C , I have isolated the problem to the fact that the data is being sent as one packet to the iPhone. Upon printing out my generated string when the data is received, the string 233! is received all at once rather than individual chars of 2 3 3, and one second later the signal to clear, !. The data takes two seconds to appear on my phone, indicating that both delays are being used. I need a way to separate the 2 3 3 packet from the ! packet.

Answer 1

First off, this line:
NSLog([NSString stringWithFormat:#"%#",d]);
Is sort of pointless. The stringWithFormat serves no real purpose, since NSLog takes a format string anyway.
Use this instead:
NSLog(#"%#", d);
You should probably also log the contents of "s" once you convert your NSData to an NSString. That will help you figure out what's going on.
What is likely going on is that your string is coming in as "233!", all together, 4 bytes at a time (assuming that your integer is == 233).
Your string is unlikely to ever contain just "!". Instead, it will likely contain "233!" (4 characters.) I say likely because it depends on how the data is packetized into BLE. Something that short should be sent all in 1 BLE packet, so you should get the entire string together.
You could use the NSString method rangeOfString: to search for your "!" string, and if it contains an "!", clear your label, but that won't really do any good either. If you're sending "233!", then the iOS code will see the exclamation point in the string it receives and simply clear the label.
Or does your arduino project first send "233", then after some other event, send the "!". You didn't make that clear.
Another problem: What does the Arduino String class do if the integer is less than 1000, or less than 100, and doesn't require 3 or 4 characters to convert to a char array? What is stored in the unused bytes? You're always sending 4 characters, which is probably wrong.

Answer 2

Adding in another ble_do_events(); after calling the sendMyInt(); function causes the data to be transmit in two separate packets.