Need to save power


#1

If I want to save power and I’m not using certain features of the 410E, could I not apply power to, for example, the RF side of the chip? Or is their a disable function that essentially does the same thing?


#2

Hi @Wale:

The Snapdragon chipset has many power saving features since it was originally designed for a battery powered cell phone. The Android software will turn off many subsystems inside the chip (The Debian software does some of this too) including reducing clock speeds, powering down CPUs, turning off WiFi, reducing drive strength on GPIOs while sleeping, DRAM in self-refresh, eMMC powered down, etc. However the DragonBoard 410c was not designed to optimize power, there are some things which can’t be shut down such as the MIPI-DSI to HDMI transmitter chip, and the USB Hub, the 12V to 5V step down was selected for wide range, not high efficiency. The software you are running has a huge effect on overall power consumption of the board. The 410E chipset can get to extremely low power levels when everything is shut off and it is sleeping.

Full Disclosure: I am an employee of Qualcomm Canada, any opinions expressed in this or any other posting may not reflect the opinions of my employer.


#3

Sorry, I may not have mentioned this but I am working on a class project, in which i’m developing a custom PCB based on several circuits in the dragon board. I’m essentially shrinking down the dragon board to fit onto an eyeglass. So, in light of this, could I not power many of the circuits within the processor that i don’t care about, such as the bluetooth, gps and rf circuits?


#4

If you turn off WiFi, Bluetooth, or GPS in the settings, then the OS will automatically power down the circuitry. No need to do anything else.

As a side note: If you are designing your own PCB, you must be VERY careful with the circuit layouts, particularly the power traces and the high speed connections. If your CAD tools cannot simulate signal integrity and compute impedance vs frequency plots of the power traces the board will not work. Please read the APQ8016E design guidelines https://developer.qualcomm.com/hardware/snapdragon-410/tools

A better way to do this is to buy a SOM (System On Module) that is already tested. Checkout the SOMs from Intrinsyc, and InForce Computing. The SOM will be significantly less expensive than the set-up costs for a 8 to 10 layer PCB.

Full Disclosure: I am an employee of Qualcomm Canada, any opinions expressed in this or any other posting may not reflect the opinions of my employer.