something wrong SPIS communication...

[KorJH]

Hello, 

My project is displaying ADC datas, Real-time based.

ADC : ADS7054.

SDK : 17.1.0 nRF5 SDK

softdevice : s140

chip : nrf52840

Master Boards SPI Timing : (below images) **

I use SPI packet size 8bit.

2*packet define 1ADC data(14bit). 

1 Sample is 2packet.

ADC data read from other boards, which is spi Master board.

spi Master board send datas, Format is SPI_MODE 0.

SPI_MODE Setting : //infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.nrf52832.ps.v1.1%2Fspi.html

 

I just merged 2 example projects,  ble_app_uart and spis.

and testing in 1-kHz signal, graph is very rough..

*Every 120 Samples, loss some datas.

After BLE communication,  data plot is below. (using MATLAB)

In debug terminal SPI buffer data plot is below. 

plots are same... 

i think this means

something caused in SPI communication..

this is my Spi & ble sending code. SPI instance is 1.

I want Sampling 10-kHz sinusoidal signals and plotting in real-time, SPI + BLE copmmunication.

Thank you.

[Vidar Berg]

Hello,

The first thing I would suggest you do is to check the return code from ble_nus_data_send() to find out if your Bluetooth link is able to keep up with the sample rate.

e.g.

err_code = ble_nus_data_send(..);
if (err_code != NRF_SUCCESS) 
{
    NRF_LOG_INFO("Failed to send notification. (0x%x)", err_code);
}

Best regards,

Vidar

[KorJH]

Hello,

I am check with this code,

I found many losses in BLE.

How can i increase BLE throghput?

Thank you. 

[Vidar Berg]

Hello,

The max. throughput you can get with the Softdevice is shown in the specification here: Bluetooth Low Energy data throughput. Although this is likely to be limited by your central (PC). 

Does the data packet length get increased in your gatt_evt_handler() callback after the connection is established? In any case, the throughput will become better if you can fill the full packet length (m_ble_nus_max_data_len) with multiple ADC samples instead of sending only one sample in each notification packet.

You may also want to increase the hvn_tx_queue_size via the sd_ble_cfg_set() API in ble_stack_init(). This will allow you to queue up more notification packets before ble_nus_data_send() starts returning NRF_ERROR_NO_MEM.