Question

I’m trying to make an app that communicate iPhone with another hardware using dock to RS232 wire (I bought from RedPark). I’m also using the library provided by redpark. I made a simple code at beginning, it worked fine.
UInt8 infoCmd[5] = {0x3E,0x3E,0x05,0x80,0xff};
[rscMgr write:infoCmd Length:5];
Then I want to add more command to it, so I create a method that returns different combinations of command I need.

- (UInt8 *)requestCommand:(int)commandName{
    UInt8 * command;
    if (commandName == DATADUMP) {
        command=[Communication buildDataDump];
    }
    if (commandName == GETSERIALINFO) {
        command=[Communication buildGetSerailInfo];   
    }
    return command;
}
+ (UInt8 *)buildGetSerailInfo{
    UInt8 *command = malloc(sizeof(UInt8)*5);
    command[0]=SYN;
    command[1]=SYN;
    command[2]=ENQ;
    command[3]=GETSERIALINFO;
    //command[4] = {SYN, SYN, ENQ, GETSERIALINFO};
    return command;    
}

The thing is, some of my commands includes data that can be 200 bytes long. How can I create an UInt8 array that is easier for me to add bytes?
I’m new to programming, please explain to me in detail. Thank you a lot in advance.

Answer 1

Actually you will just send data, row byte over the wire. I do something similar in one project (not wire, but RS232 commands over TCP/IP), and it becomes quite simple, if you use an NSMutableData instance.

A snippet from my code:

static u_int8_t codeTable[] =   { 0x1b, 0x74, 0x10 };
static u_int8_t charSet[]   =   { 0x1b, 0x52, 0x10 };
static u_int8_t formatOff[] =   { 0x1b, 0x21, 0x00 };
static u_int8_t reverseOn[] =   { 0x1d, 0x42, 0x01 };
static u_int8_t reverseOff[]=   { 0x1d, 0x42, 0x00 };
static u_int8_t paperCut[]  =   { 0x1d, 0x56, 0x0 };  


NSMutableData *mdata = [NSMutableData dataWithBytes:&formatOff length:sizeof(formatOff)];
[mdata appendBytes:&formatOff length:sizeof(formatOff)];
[mdata appendBytes:&reverseOff length:sizeof(reverseOff)];    
[mdata appendData: [NSData dataWithBytes: &codeTable length:sizeof(codeTable)]];
[mdata appendData: [NSData dataWithBytes: &charSet length:sizeof(charSet)]];

As you see, I am just appending the data byte by byte.