How to DECLARE - ATT_MTU, PHY, LE Data Length, LE Connection interval for nRF5340 DK?

[StefiNR]

The board is nRF5340 DK.

nRF Connect SDK1.8.0 / Windows

Example Peripheral UART.

 

I want to DECLARE them, not change them with different types of functions. There are examples for the second. I want to compile the project directly with these values. I know that then the individual devices will be understood each other, for the specific values. Everywhere in the examples are used functions that change in the process of work, I do not want that. I don't care how this happens in the different SoftDevices.

 

I want to change the default ones.

BT_LE_CONN_PARAM_DEFAULT

Default LE connection parameters: Connection Interval: 30-50 ms Latency: 0 Timeout: 4 s

Enable LE Data Packet Length Extension.

 

How and where to declare them?

[Hung Bui]

Hi Stefan,

Could you let me know if you have control over both sides of the connection or not ? (central and peripheral) 
I assume you want to just use the configuration and don't want to change the configuration in run time ? 

Note that most of the parameter of a connection is dictated by the central device. For example the connection parameter need to be configured (for example: connection parameters) and feed to the stack via bt_conn_le_create() function. 

Have you looked at the configuration in prj.conf of the throughput example ? 

[StefiNR]

I have been studying this example for 3 days, this is not my case. That's why I wrote that I don't want that. I have two kits, nRF5340 DK, the communication for the test will be between them. I want to see what speed I can get. I changed the software inside the central and peripheral (UART) to be completely binary. It exchanges commands up to 40 bytes long.

The situation is as follows. / If I call them briefly like this:/

1/ Central is s wireless port on a machine. Send/Receives commands through uart.

CU(central uart), CP(central processor/ nRF5340), CB(central Bluetooth)

2/ The peripheral is a remote control, there is a version with a display. In this case, a second processor (Big) is connected to the serial port, which controls the display. It turns on about twice a second and paints the screen. nRF5340 (it is actually the remote) reads all inputs (buttons, switches, joystick, etc.) and controls some LEDs/outputs.

PU(peripheral uart), PP(peripheral processor/ nRF5340), PB(peripheral Bluetooth)

 

Several cases.

1. The machine sends status to the remote.

CU>CB>>PB>PU or PP. The indication is on the display or on something on the remote control (LED)

2. The machine reads the status of all inputs on the remote control.

CU>CB>>PB>PP>PB>>CB>CU - Returns an answer.

3. The machine exchanges data directly with the second processor with the display.

CU>CB>>PB>PU> Display>PU>PB>>CB>CU - Returns an answer.

….

And so many options.

 

I need to achieve about 5-6 commands (* 40 bytes) with return response !! , 5-10 times per second.

At the moment I have tried all this and it works, but the times are very big.

 

I even did such a test:

CU>CB>>PB>PP>PB>>CB>CP>CB>>PB>PP>PU for one command.

At the moment, all this works on cable (RS-485), the idea is not to get worse. If it gets better, even better. :)

[Hung Bui]

Hi, 
I think for that you just need to configure the connection interval as low as possible (but not too low as it will draw more current). 
Please set the INTERVAL_MIN and INTERVAL_MAX on the central side to 0x28 (50ms) to test. 

This intervals should be used in the .conn_param when you scan or when you connect. 

Also in the project configuration please set: 

CONFIG_BT_BUF_ACL_RX_SIZE=251
CONFIG_BT_ATT_PREPARE_COUNT=2
CONFIG_BT_CONN_TX_MAX=10
CONFIG_BT_L2CAP_TX_BUF_COUNT=10
CONFIG_BT_L2CAP_TX_MTU=247
CONFIG_BT_CTLR_RX_BUFFERS=2
CONFIG_BT_BUF_ACL_TX_COUNT=10
CONFIG_BT_BUF_ACL_TX_SIZE=251
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

In the child_image\hci_rpmsg.conf please set:

CONFIG_BT_BUF_ACL_TX_SIZE=251
CONFIG_BT_CTLR_DATA_LENGTH_MAX=251
CONFIG_BT_BUF_ACL_RX_SIZE=251

[StefiNR]

I'm not sure I understood what needed to be done.

1. About INTERVAL_MIN and INTERVAL_MAX.

In central main.c ONLY:

 // ADDED *****

#define INTERVAL_MIN   0x28     

#define INTERVAL_MAX  0x28     

static struct bt_le_conn_param *conn_param =

                BT_LE_CONN_PARAM(INTERVAL_MIN, INTERVAL_MAX, 0, 400);

// ADDED *****

 

In

static int scan_init(void)

{

                int err;

                struct bt_scan_init_param scan_init = {

                               .connect_if_match = 1,

                               .conn_param = conn_param // ADDED ****

                };

….

 

Something else somewhere ??

 

No difference. Sending and returning a command between the two boards is about 100ms.

CU>CB>>PB>PP>PB>>CB>CU

I tried to change the values (MIN/MAX), nothing different. Something else needs to be set somewhere.

 

2. CONFIG..

 This need to add ONLY in central or and in peripheral?(I tried both options. no difference.)

As far as I understand this only changes the buffers, without affecting the times.

In prj.conf file.

CONFIG_BT_BUF_ACL_RX_SIZE=251

….

CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

 

In central ONLY child_image\hci_rpmsg.conf is missing.

The only file inside is this rpc_host.conf. (\SDK\ncs\v1.8.0\nrf\samples\bluetooth\central_uart\child_image)

In it I added:

CONFIG_BT_BUF_ACL_TX_SIZE=251

CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

CONFIG_BT_BUF_ACL_RX_SIZE=251

From VSC:

CONFIG_BT_CONN_TX_MAX=10
CONFIG_BT_L2CAP_TX_BUF_COUNT=10

meaningless, these are the default values

CONFIG_BT_CTLR_RX_BUFFERS=2

CONFIG_BT_CTLR_RX_BUFFERS couldn't be set. Missing dependencies:BT_CTLR

CONFIG_BT_CTLR_DATA_LENGTH_MAX=251

CONFIG_BT_CTLR_DATA_LENGTH_MAX couldn't be set. Missing dependencies:

BT_CTLR_DATA_LENGTH && BT_CTLR

From my first post:

BT_LE_CONN_PARAM_DEFAULT -> Connection Interval: 30-50 ms

That is, setting 50 ms should not affect. But obviously the set does not affect, because when reducing to 10ms, the times are the same.

Somewhere I'm wrong in principle.:(

[Hung Bui]

Hi, 
To be able to know what wrong, I would suggest to capture a sniffer trace. 
With that we will be able to see very easily what caused the issue and why it take a long time for the returning command

(Note that if it require a packet back and forth then it may take 2 connection interval meaning 50x2  = 100ms) 

Please download the sniffer software here and use a DK as the sniffer. Please follow the documentation on how to track a connection.

[StefiNR]

As far as I can see, for some reason the standard times of 30-50 ms are returning.

q_00.zip

[Hung Bui]

Hi Stefan ,

It was because the peripheral requested the connection parameter. ...

If you configure this: 

CONFIG_BT_GAP_AUTO_UPDATE_CONN_PARAMS=n

on the peripheral side it will not request that again.