CC2538 Current values for energy computation

Alessandro Musi

Other Parts Discussed in Thread: CC2538

Hi,

I'd like to know the power consumption of my cc2538 running a CoAP server taken from cetic/6lbr repo (a Contiki OS branch).

The mote is attached to the TI SmartRF06 (the open-base on the right)

and the base is connected through usb cable (attached to my mac) in the usb 3.0 port.
I've followed this guide

https://thingschat.blogspot.com/2015/04/contiki-os-using-powertrace-and.html#comment-form

and got the four parameters:

ALL CPU (the total number of ticks for CPU in active mode), ALL LPM (the total number of ticks in Low Power Mode), ALL TX (Transmit) and ALL RX (Receive).

For the total energy there's a formula which requires Voltage and the current of all 4 components (CPU,LPM,TX,RX).

I've checked the cc2538 datasheet

http://www.ti.com/lit/ds/symlink/cc2538.pdf

and from what I get the RX current is 20mA, and the TX current is 24mA. What about CPU and LPM?

Thanks

over 7 years ago

0 Fredrik K over 7 years ago

TI__Guru** 106705 points

Hi Alessandro,

In section 5.4, the two first parameters is current consumption for CPU only. LPM current is listed a few places down in the same table.

You can also take a look at this application note for a practical approach: www.ti.com/.../swra347

Cheers,
Fredrik

0 Alessandro Musi over 7 years ago in reply to Fredrik K

Prodigy 40 points

Hi Fredrik,

thanks for your reply.

So basically the parameters are:

Voltag=3V

TX=24mA

RX=20mA

CPU=13mA

LPM=0.4mA

Sorry to bother but I need the precise value to use the formula.

Thanks

0 YiKai Chen over 7 years ago in reply to Alessandro Musi

Guru 735685 points

There are 3 low power modes, PM1, PM2, and PM3 which consumes different currents. By the way, different TX power would consume different power. 24mA is when TX power is 0 dbm. If you set different TX power, it would be different.

0 Alessandro Musi over 7 years ago in reply to YiKai Chen

Prodigy 40 points

Thanks for your reply YiKai Chen,
for the LPM parameter how do I know the actual mode (PM1, PM2, PM3)? And for TX how to know if 0 db 7db?

0 YiKai Chen over 7 years ago in reply to Alessandro Musi

Guru 735685 points

Those depend on your application so you should check how your application configure them.

0 Alessandro Musi over 7 years ago in reply to YiKai Chen

Prodigy 40 points

The examples is this one

https://github.com/cetic/6lbr/wiki/Example-:-DTLS-CoAP-Server

and the code location this one

https://github.com/cetic/6lbr/tree/develop/examples/6lbr-demo

I didn't find anything in the 6lbr-demo project_conf.h regarding the LPM or TX, so I searched inside the platform folder

https://github.com/cetic/6lbr/blob/develop/platform/cc2538dk/

Inside contiki-conf.h at line 313

The SoC will never drop to a Power Mode deeper than the one specified here.
* 0 for PM0, 1 for PM1 and 2 for PM2
*/
#ifndef LPM_CONF_MAX_PM
#define LPM_CONF_MAX_PM 1
#endif

#ifndef LPM_CONF_STATS
#define LPM_CONF_STATS 0 /**< Set to 1 to enable LPM-related stats */
#endif
/** @} */

basically the mote never go deeper than PM1, since is not specified in the project file do I have to assume that the mote works in PM1 hence 0.6 mA?

Can't find nothing related to the other parameters (CPU, TX, RX).

0 YiKai Chen over 7 years ago in reply to Alessandro Musi

Guru 735685 points

Cannot help you to check the code and suggest you to use power analyzer or scope to measure/monitor power consumption for better understanding how your application consumes power.

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CC2538 Current values for energy computation