CryptoCell Energy Consumption

[scvdevel]

Hello,

I am in the process of evaluating the '840's BLE and CryptoCell for a low power application. I am using a modified version of the ble_app_template example, with custom characteristics/services and the CryptoCell library. I am to successfully encrypt and decrypt data using AES in the CryptoCell. I am using SDK 14.2 and Keil uVision 5.23.0.0.

When measuring current consumption, I've noticed that the background current is ~6-7 mA. After commenting out all CryptoCell routines, I noticed that background current drops to ~0.5 mA. After some investigation, I found that calling SaSi_LibInit() results in the excessive current draw. Calling SaSi_LibFini() does not reduce the excessive current draw. It seems like calling CRYS_RND_Instantiation() results in the excessive current draw. 

Is there something I need to do to reduce the current draw when using the CryptoCell?

Thanks!

[redsun]

Cryptocell always draw a bunch of energy, because of massive computing. Set a system timer and turn on Cryptocell accelerator when you need, this workaround slightly decreases overall system reaction (in my project i got 10-15% longer system response), but gives significantly more operation time from powersource.

[scvdevel]

Thanks for the suggestion. I tried enabling/disabling the CryptoCell when it's needed, but current draw remains high even when turn it off.

[redsun]

Did you reboot transceiver after disabling CryptoCell?

[scvdevel]

No, I have not. I do not want to kill the connection when I disable the CryptoCell. 

[redsun]

Well, i know that it sounds shitty, but i do not see any other option than use external uC with cryptographic engine.

May be in mass production release it will be fix in silicon.