ble data transfer

RE: ble data transfer

tesc — Wed, 29 Jun 2016 11:38:24 GMT

Hi,

Fist we must distinguish BLE and the Nordic UART Service (NUS).

NUS is only a service, which provides UART over BLE. Since it works as UART, it can be used as UART. Basically you send and receive a series of bytes.

There are several other BLE services. Some are specified by the Bluetooth SIG, others are custom made. So in theory you could make your own service, or select an existing one, that fits with your use case. See BLE Services, a beginner's tutorial for an introduction to services.

If you want to use the Nordic UART Service, i.e. UART communication, you must decide how to encode your numbers. You may send integers and floats by just using their binary values, splitting them up into a series of bytes as suggested by RichieJH. Another solution is to use sprintf() to create a string from the numeral value and transmit that string.

Regards, Terje

RE: ble data transfer

awneil — Wed, 29 Jun 2016 10:09:06 GMT

Look at the function prototype, and read the documentation!

The 2nd parameter must be a pointer, and the third is the length of the data that you are sending - isn't it?

RE: ble data transfer

Siva — Wed, 29 Jun 2016 09:59:37 GMT

Suppose if I want to send the variable on ble (float Temp = 12.345;) Can I still use (error_Code = ble_nus_string_send(&m_nus,Temp,20);) ? I presume it should be a different function.

RE: ble data transfer

awneil — Wed, 29 Jun 2016 09:36:56 GMT

Of course, this all assumes that the OP is OK with binary data...

RE: ble data transfer

awneil — Wed, 29 Jun 2016 08:56:16 GMT

That's better!

www.ibm.com/.../cplr068.htm

RE: ble data transfer

RichieJH — Wed, 29 Jun 2016 08:53:41 GMT

Amended the answer above to apply bit masking and shifting.

RE: ble data transfer

awneil — Wed, 29 Jun 2016 08:34:28 GMT

Of course it does!!

RE: ble data transfer

RichieJH — Wed, 29 Jun 2016 08:21:20 GMT

Actually, you might be right. I've just noticed my values never been larger than one byte so while it compiles fine and appears to work, what is happening is the value is being assigned to that array element and when putting in a value greater than one byte it is being lost.

RE: ble data transfer

RichieJH — Wed, 29 Jun 2016 07:43:23 GMT

Of course it does, have you actually tried it? I have and it works. So unless my compiler and SDK has magical powers I'm not sure why you are insisting it doesn't.

RE: ble data transfer

awneil — Wed, 29 Jun 2016 07:41:12 GMT

No! that is not the way 'C' works!!

When you assign to Name3[x] you are just assigning to that one element - using the standard 'C' conversion rules if the RHS of the assignment is not the same type as the LHS.

It does not run-on to subsequent elements in the array!!

RE: ble data transfer

RichieJH — Wed, 29 Jun 2016 07:24:15 GMT

You do not have to copy each byte individually and this does work.

unint32_t some_int = 100; Name3[0] = some_int;

The next 4 bytes in the array will be taken up with some_int with the value of 100. Not the most efficient way to store the value of 100, but the principle works. Remember Name3 is a Uint8_t array.

RE: ble data transfer

awneil — Wed, 29 Jun 2016 07:00:56 GMT

That won't work - you can't just do

 Name3[1] = uint32_t some_int; 
 Name3[5] = uint16_t something_else;

You have to copy each byte individually

RE: ble data transfer

RichieJH — Tue, 28 Jun 2016 23:16:08 GMT

So assume you want to send a uint16_t value of say 10000. This is of course two bytes and you must assign each byte of value to each element of the array Name3. One fairly easy way to do this is bit masking and shifting. So do this:

Name3[0] = (value & 0xFF00) >> 8;
Name3[1] = (value & 0x00FF);

Now say value was a unit32_t, which is 4 bytes long, then do this

Name3[0] = (value & 0xFF000000) >> 24;
Name3[1] = (value & 0x00FF0000) >> 16;
Name3[2] = (value & 0x0000FF00) >> 8;
Name3[3] = (value & 0x000000FF);

RE: ble data transfer

awneil — Tue, 28 Jun 2016 19:44:35 GMT

I am unable to send integers and floating values

What did you actually try?

The Nordic UART Service - like a real UART - actually just sends bytes: it neither knows nor cares whether those bytes are to be interpreted as a string, an "integer" (whatever that might mean), a "floating value" or whatever.

The documentation is here:

developer.nordicsemi.com/.../a01011.html

You just tell it where the data starts (that's the pointer), and how many bytes to send ...