ble_blinky

[s_sen]

HELLO SIR 

we are working on our current project on bluetooth .we are currently trying to broadcast data over bluetooth from one DK to others . we are trying to modify the ble_multilink_central example , and the ble blinky . the problem i am facing is to figure out the received buffer . it would be really helpful if you could point me as to where exactly is the received buffer stored .

SEGGER V3.50,      SDK 15.0,   DK Rigardo BMD300.

[MartinBL]

Hi,

In the BLE Blinky example the LED characteristic value is stored in a portion of RAM that is controlled by the softdevice. I.e. you are not allowed to access it directly, but you can use functions like sd_ble_gatts_value_get() and ..._set() to get or set the value. As in most of the BLE services in the SDK, there is a function called on_write() inside ble_lbs.c which is called whenever data is written to any of the characteristics. 

[s_sen]

ok thank you for the info, 

but could you be more specific , the function here is nrf_ble_gatt_att_mtu_central_set() & nrf_ble_gatt_att_mtu_peripheral_set(), i am using  SDK v15.0

[MartinBL]

Hi,

The nrf_ble_gatt_att_mtu_xxxxxxx_set() functions are used to set the Maximum Transmission Unit (MTU) size on the attribute layer of the BLE stack. The MTU size dictates how many bytes you can fit into a packet on the attribute layer and has nothing to do with where the receive buffer is stored or who to get it. I don't think I understand your original question. What do you mean by "figure out the received buffer"? Can you describe in more detail what you want to achieve, what you have tried, and what happens? 

[s_sen]

thank you for your reply 

we are trying to send our own data , and also extract it . so i need to figure out where is the data being stored and then copy that data in a variable for further implementations. 

so i am trying to broadcast data from ble multilink like this , and now i am trying to find out where is the data received . 

we are not passing any huge strings as data , just some integer values ....

we are using multilink  and blinky for broadcasting the values

[MartinBL]

When you write data to the Blinky peripheral a function called ble_lbs_on_ble_evt() will be called. This function in turn calls on_write() where the data is processed and forwarded to your led_write_handler function. In that function you will find a pointer to the the data:

If you want to transfer a more generic type of data, then maybe it would be better to look at the UART/Serial Port Emulation over BLE example, and see how the data is received there. 

[s_sen]

Thank you for your time 

the data in the handler is the processed data i.e, led status 0 or 1 , i am trying to access the raw data. 

the whole data frame that has been transmitted

[MartinBL]

Can you show me your code?

p_evt_write->data gives you a pointer that points to the first byte in the received data.

p_evt_write->len gives you the length of the received data. 

[s_sen]

i am trying to print the data 

and here too 

the data is just 1 or 0 

[MartinBL]

And what data do you transmit? 

p_evt_write->data[0]     -> Gives you the value of the first byte in the receive buffer

p_evt_write->data         -> Gives you a the address of the first byte in the receive buffer

If you expect more than one byte you might need to print 

p_evt_write->data[1]

p_evt_write->data[2] 

... and so on. 

[s_sen]

i am running the SDK  ble_multilink_central with ble_blinky i am expecting to see a frame of this format 

PREAMBLE | ACCESS ADDRESS | LL HEADER | DATA | CRC |

[MartinBL]

In your other case (#213381) it looks like you haven't quite figured out how to write data yet. I suggest we clear that up before we continue here.