Send 16 bits instead of 8 bits over BLE

RE: Send 16 bits instead of 8 bits over BLE

Stian Røed Hafskjold — Fri, 10 Nov 2017 14:23:39 GMT

Ok, I'm glad it worked :)

RE: Send 16 bits instead of 8 bits over BLE

Awi — Fri, 10 Nov 2017 14:19:20 GMT

Hi Stian, both your answers helped. Thank you very much. My other side was f***ing up. Sorry!

RE: Send 16 bits instead of 8 bits over BLE

Awi — Thu, 09 Nov 2017 11:11:46 GMT

Hi Stian,

Thank you for your help and time. Unfortunately, your solution doesn't work. I'm not getting any errors, but all I am receiving is value 44. Explanation of what I mean: I have an uint16_t value in my embedded software set to constant 300 (for test). I have split it into two bytes (as mentioned above) and sending it like you told me to. I'm receiving 44 (not 300) so it's basically either staying on uint8_t or doesn't send a part of the array! ... I'm out of ideas :'(

RE: Send 16 bits instead of 8 bits over BLE

Stian Røed Hafskjold — Tue, 07 Nov 2017 13:04:29 GMT

I think the easiest way to debug this is to use the nRF Connect software, either on a computer or the Android/iOS version. You can get it from google play or app store. Then you can connect to the device, discover the services/characteristics and read out the value of the characteristc. And a lot more.

RE: Send 16 bits instead of 8 bits over BLE

Awi — Tue, 07 Nov 2017 12:34:35 GMT

Hello Stian,

Thank you for your answer. Due to complexity of the code because of the previous developer, I managed to do what you said in both answer. I am not sure how I can check if the correct data is sent. Do you have any methods?

Otherwise, If I am able to fix the receiver correctly (C#, to interpret the data), I can mark one of your answers as the correct one.

I will let you know when I have finished it (due to limited time to work on this project it can have some delay)

RE: Send 16 bits instead of 8 bits over BLE

Stian Røed Hafskjold — Tue, 07 Nov 2017 11:11:43 GMT

Error 12 is NRF_ERROR_DATA_SIZE. So a data size of 2 is probably too big for the characteristic. When you add the characterisic using the sd_ble_gatts_characteristic_add() function, you specify the attribute max length in the attr_char_value. Maybe this is set to 1. Look for attr_char_value.max_len or similar in the code.

RE: Send 16 bits instead of 8 bits over BLE

Awi — Fri, 03 Nov 2017 11:13:52 GMT

So I tried doing this:

uint16_t val = 300;
static uint8_t data[2];
data[0] = (uint8_t)(val >> 8);
data[1] = (uint8_t)(val);
update_characteristic(conn_handle,value_handle, sizeof(data),(uint8_t*)data)

and in update_characteristic:

gatts_value.offset = 0;
gatts_value.len = len;
gatts_value.p_value = data;
err_code = sd_ble_gatts_value_set(conn_handle, value_handle, &gatts_value);
APP_ERROR_CHECK(err_code);

Still getting error at the app error check:

APP ERROR: 12, line: 105, file .....

What am I doing wrong?

RE: Send 16 bits instead of 8 bits over BLE

Stian Røed Hafskjold — Thu, 02 Nov 2017 11:36:15 GMT

If you want the attribute value to be two bytes (16 bits), set the len value to 2 and represent the data as an uint8_t array with size 2.

How you choose to split the 16 bits and put them in to the array is up to you, as long as the reciever is able to decode it.

Yes, the other side will have to decode this and represent it as needed.

RE: Send 16 bits instead of 8 bits over BLE

Awi — Thu, 02 Nov 2017 08:20:43 GMT

I just cast is using (uint8_t *) But I figured, I might have to do something like

data = val>>8 then send then data=val then send again

the other side will have to interpret different too. Is that correct?

RE: Send 16 bits instead of 8 bits over BLE

Stian Røed Hafskjold — Wed, 01 Nov 2017 11:59:33 GMT

Can you please show us how you convert the 16 bits data too?
p_value is supposed to be a pointer to an uint_8 array. So you need to split the 16 bits into two bytes in an array. infocenter.nordicsemi.com/.../structble__gatts__value__t.html