Calling curl command using byte buffer in Arduino

Question

I'm currently working on Arduino devices and tying to use "process library" to call my REST API. Here's my code snippet.

void api_send_cell(uint8_t* data)
{
    Process p;    
    p.begin("curl");
    p.addParameter("-X Post");
    p.addParameter("-H content-type: multipart/form-data");
    p.addParameter("-k " + url);
    p.addParameter("-F data=");
    p.addParameter(buf);
    p.run();
}

But the thing is that my data (uin8_t buffer) is a series of raw data which are just numbers from 0 to 255. Because the process needs string for parameter just like real command, I couldn't just put my data to addParamter function.

So, I think I have to convert those bytes to string representation (for example, hex string) somehow.

Is there any solution for this problem?

do you have a Yun board? this is not the way to do network communication in Atmega of Arduino Yun. use the Bridge library. — Juraj, Nov 23 '18 at 09:01
You can improve your question by specifying the format of the string you need. Should the numbers be separated by spaces, commas, tabs, or something else? — jfowkes, Nov 23 '18 at 12:08
@Juraj I'm using dragino LG01, and I thought it is ok to use process library because there are some example codes using that library. — goofcode, Nov 23 '18 at 17:22

score 0 · Accepted Answer · answered Nov 23 '18 at 12:04

0

You need to use sprintf to convert your uint8_t data to a string:

char string_data[LENGTH]; // LENGTH = Whatever length is sufficient to hold all your data
int i=0;
int index = 0;
//NUMBER_OF_ITEMS_OF_DATA could be constant or another variable
for (i=0; i<NUMBER_OF_ITEMS_OF_DATA; i++)
{
   index += sprintf(&string_data[index], "%d,", data[i]);
}
p.addParameter(string_data);

This will convert an array like {1,2,3,4,5} into the string "1,2,3,4,5,".

You can change the "%d," in the sprintf call to get another format. You may also want to remove the trailing , depending on your requirements.

answered Nov 23 '18 at 12:04

jfowkes

1,495
9
17

Thank you for answering. Well, this is good enough. What i was trying to do was sending raw image data which uses a byte for a pixel. I was wondering if there is any way to send byte array itself, because it is lot easier to handle on server side and doesn't require any parsing process. – goofcode Nov 23 '18 at 17:28
Yeah, if you have zeros in your data you'll need to encode them somehow because HTTP is text-based and will interpret actual zero-bytes (0x00) as NULL. I'm not qualified to say what happens next, but it likely won't be what you intend. – jfowkes Nov 25 '18 at 22:09
Great, I decided to use hex because Arduino has String data type that gets byte and convert it to hex string. Thank you by the way. – goofcode Nov 26 '18 at 02:38

Calling curl command using byte buffer in Arduino

1 Answers1