gistfile1.rb

requestData = NSString.alloc.initWithData("STS\r", encoding:NSUTF8StringEncoding)
sample_request = ORSSerialRequest.requestWithDataToSend(requestData, userInfo: '', timeoutInterval: 3.0, responseEvaluator:-> inputData { return true })
@serial.sendData(sample_request)

gistfile2.m

NSData *requestData = [@"data?" dataUsingEncoding:NSASCIIStringEncoding];
ORSSerialRequest *request = 
    [ORSSerialRequest requestWithDataToSend:requestData
                                   userInfo:nil
                            timeoutInterval:2.0
                          responseEvaluator:^BOOL(NSData *inputData) {
                              if ([inputData length] != 8) return NO;
                              NSData *headerData = [inputData subdataWithRange:NSMakeRange(0, 4)];
                              NSString *header = [[NSString alloc] initWithData:headerData encoding:NSASCIIStringEncoding];
                              return [header isEqualToString:@"data"];
                          }];