Increase Notification Frequency nrf51422

RE: Increase Notification Frequency nrf51422

Stian Røed Hafskjold — Wed, 12 Dec 2018 17:01:54 GMT

So the peripheral device is the slave device when you look at the physical radio layer. This means that RX is turned on first, then TX. What happens is that it transmits on TX, waits one connection interval, it gets the ACK on RX, which is the BLE_EVT_TX_COMPLETE event. By the time the application finishes setting up the notification packet, the radio has already transmitted an empty packet on TX, and is waiting for the next connection interval to transmit the notification packet.

So the method takes two connection intervals to transmit the packet. So when you connect to the cell phone it sets the interval to 15ms. This goes up into 30ms (every other connection interval), 45ms and 60ms. The reason why it's not consistent on 30ms is because you get packet loss, which happens from time to time, and a retransmission of the last packet.

You can try to use radio notifications instead. With radio notifications you can set it up to trigger on an event X number of milliseconds before the actual radio event (connection event) and call the hrs send function.

You should also look into using the nRF sniffer. It's a great tool for debugging. It allows you to sniff the packets on air, so you can see what is actually going on.

RE: Increase Notification Frequency nrf51422

Pablo G — Sun, 09 Dec 2018 01:52:26 GMT

For the moment I'm testing my code using the nRF51 DK board by connecting it with my phone. On the nrfConnect mobile app, I found "Request connection priority" which can be set HIGH (11.25-15ms), BALANCED(30-50ms), LOW POWER(100-125ms). After I set to HIGH option, I can see through the gpio pin that TX speed has increased from 90 ms to 30 ms. However, I'm still getting variations on the sending frequency (Sometimes is not 30 ms interval but 60.3 or 45.4ms):

I understand the period of BLE_EVT_TX_COMPLETE may not be the adequated because of my central's configuration, but what I don't understand is the variations on the sending frequency. Do you think may be a central problem or the peripheral is not well configured? (I'm uploading my peripheral main.c and service (I used a modified version of the ble_hrs file) to the post)

ps. Thank you for helping me solve this problem, I've spent so many hours and I'm running out of ideas to solve this issue :)

RE: Increase Notification Frequency nrf51422

Stian Røed Hafskjold — Fri, 07 Dec 2018 12:27:18 GMT

Are you sure the connection interval is actually 10ms? In the end it is the central device that decides the connection interval. If you connect using nRF Connect, you can set the connection interval directly. Click on the settings icon -> Update connection.

RE: Increase Notification Frequency nrf51422

Pablo G — Thu, 06 Dec 2018 21:32:51 GMT

I tried what you proposed. Toggle extends the time to '1' of the gpio, but the period is still way far from 10 ms and it is not constant: 90ms, 90ms, 90ms, 135ms, 90ms, 90ms, 90ms, 90ms, 90ms, 135ms,

RE: Increase Notification Frequency nrf51422

Stian Røed Hafskjold — Thu, 06 Dec 2018 12:42:47 GMT

Can you try to use nrf_gpio_pin_toggle(14); instead of nrf_gpio_pin_set(14);nrf_gpio_pin_clear(14);

I have a feeling that the pin toggling is too fast for the logic analyzer