CPU Unblocking, BLE Radio Notification and pStorage Access

RE: CPU Unblocking, BLE Radio Notification and pStorage Access

sam wagner — Thu, 19 Mar 2015 17:34:53 GMT

Thank you so much for the clarification. I will close the issue.

RE: CPU Unblocking, BLE Radio Notification and pStorage Access

Stefan Birnir Sverrisson — Thu, 19 Mar 2015 14:59:38 GMT

Hi Sam

With pstorage, you can safely call flash write and flash erase operations without worrying about the CPU blocking. This is handled internally in the softdevice since S110 6.0.0, see the release notes for S110 6.0.0. The flash erase operation will however take ~21ms to complete, so if you use radio notifications and have connection/advertising inerval <30ms, your throughput will be decreased when performing flash erase operations, as they might override scheduled BLE transmission. This will however not result in BLE disconnection.

When using radio notificatoins with pstorage, realise the following limiation of the softdevice:

If Radio Notifications are enabled, flash write and flash erase operations initiated through the SoftDevice API will be notified to the application as Radio Events (FORT-809).

RE: CPU Unblocking, BLE Radio Notification and pStorage Access

sam wagner — Tue, 17 Mar 2015 18:54:53 GMT

Hi Hakon, Thanks a lot for the response... Just to further understand, can we use pstorage APIs (ie sd_flash APIs) anytime without enabling radio notification even with SDK6.1? AFAIK there were problems because of the CPU blocking during Flash access in my project. And the issues went away when I started using Radio Notification feature. I am hoping that I can get away with disabling Radio Notification feature with CPU unblocking enabled in SDK7.2 in order to reduce data transfer latencies (all my data, exchanged over BLE, is stored in Flash). Let me know your input.

RE: CPU Unblocking, BLE Radio Notification and pStorage Access

Håkon Alseth — Tue, 17 Mar 2015 11:57:32 GMT

Hi Sam,

"unblocking" the CPU during connection intervals will not have any timing implications on the radio_notification. As Pstorage uses the sd_flash-API to store/erase flash, it is considered safe to use at any time (as it queues cmd's), but if you use it with combination with the radio_notification you're certain that you will have a longer period where you're not interrupted by the stack.

Cheers, Håkon