• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 98 subscribers
  • Views 413 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Accuracy of the AM335x Power Estimation tool

Matthew Schuckmann1
Intellectual 975 points
Other Parts Discussed in Thread: AM3352, AM3358

I'd like to get some feedback on how accurate the AM335x Power Estimation tool is?

We are working on a design based on the AM3352 300MHz in the ZCZ package and we'd like to know how low total board power consumption we can get with the processor still able to receive and respond to Ethernet traffic (WoL is not an option). For purposes of this estimate there isn't much on the board other than the processor 2Gbit of DDR3, 2Gbit of NAND flash, 1 Ethernet Phy/Magnetics, a serial port, and the power management IC. 

When we compare the values in the Power Consumption tables here they don't really jive with the numbers provided from the Power Estimation Tool using this input file 7217.003-am335x_pet_input.xls the results file 6864.report-003-am335x_pet_input.xls indicates that the total power is about half that from the measured values from the Power Consumption wiki and estimated power consumption for the VDD_DDR is minuscule in comparison. 

In addition the Power Estimation Tool numbers also don't really match up with simple measurements that we can take from the BBB. Again the Power Estimation tool numbers seem much lower. 

I've tried to make the BBB behave as close to our target design as possible but I haven't quite figured out how to turn off things we don't plan to use like the LCDC, SGX, USB Phy, or MMC interfaces. 

Also I haven't been able to determine if the AM3352 should consume less power than the AM3358 that is on both the BBB and the EVM boards. 

Any advice, previous experiences, tips, tricks, etc would be very helpful. 

Thanks,
Matt S. 

  • 0
    TI__Guru**** 393215 points

    Hi Matt,

    The tool, as it name says is an "estimation" tool. The figures provided in the Power Consumption Summary wiki are real world, measured off a working board.

    Basically if you don't want to use a peripheral what you can do is switch its clock off. Check section 8 of the AM335X TRM Rev. J.

  • 0 in reply to Biser Gatchev-XID
    Intellectual 975 points

    Thanks for the info Biser, I'm reading up on section 8 of the TRM now. Can you point me to any documentation on how to disable the clocks from the Linux environment. 

    i.e. Is there a /sys interface to do it? or do I need to edit the device trees, or dig into the drivers? I'm sure there is a way to do it, but as someone new to this processor and the latest Linux I don't know where to look first.

    Any help would be much appreciated. 

    Also I'd still like to hear from anyone that used the estimation tool and then built a system and how close the tool came to reality. 

    Matt S. 

  • 0 in reply to Matthew Schuckmann1
    Intellectual 975 points

    So I've done some poking and I think that I've been able to turn off the LCDC interface by editing the am335x-boneblack.dts device tree file and setting the lcdc device status to disabled. This dropped the current usage by about 50mA. 

    I verified that the clock was off by by checking the register via devmem2

    root@am335x-evm:~# devmem2 0x44e00018
/dev/mem opened.
Memory mapped at address 0xb6ff6000.
Read at address 0x44E00018 (0xb6ff6018): 0x00070000

    Interestingly if I try to turn the clock back on via:

    root@am335x-evm:~# devmem2 0x44e00018 w 0x2
/dev/mem opened.
Memory mapped at address 0xb6f48000.
Read at address  0x44E00018 (0xb6f48018): 0x00070000
Write at address 0x44E00018 (0xb6f48018): 0x00000002, readback 0x00000002
root@am335x-evm:~# devmem2 0x44e00018
/dev/mem opened.
Memory mapped at address 0xb6ff3000.
Read at address  0x44E00018 (0xb6ff3018): 0x00040002

    But don't see a similar increase in current so I suspect it takes more than just turning on or off the clock or I'm missing a lot in what needs to happen. 

    I was really hoping that there would be some examples available. 

    Matt S.