TWI High Current S110 8.0.0

[michaeld]

Hello,

I migrated my project from softdevice S110 7.1.0 on a nRF51422 FAC to softdevice S110 8.0.0 and an nRF51822 FAA G3. My code used to have a current consumption around 10 to 15 uA.

Now when I enable the TWI hardware version I get an above average current consumption.

TWI Hardware +- 1,5 mA

The TWI communication does work and all works fine but the current consumption is very high. With the software version everything is ok but I cannot configure it to use the maximum frequency of 400 kHz I get only set it to a max of 250 kHz.

I have DC/DC Enabled and integrated on my new board with the nRF51822 FAA G3.

Is this a known issue or am I forgetting something?

[Stefan Birnir Sverrisson]

Hi

When using SPI, TWI or UART, it will consume ~1mA extra current consumption when enabled. The trick is to only enable the peripherals when communication is needed. This is further explained in the current consumption guide, section "Setup of SPI, UART, TWI interfaces".

The DCDC should not be used with second revision chips and the softdevice, see this DCDC recommendation thread.

[michaeld]

Thank you for your answer.

I found different results with using the TWI peripheral. When using the TWI Hardware version on the nRF51422 FAC it did not consume an ~1 mA extra and it was always enabled (don't know how to disable it, it's not specified in the current consumption guide).

But migrating my code to the nRF51822 FAA G3 also with S110 7.1.0 I have this extra ~ 1 mA extra current consumption. And when I use the software version current consumption is lower but still higher then used on the nRF51422 FAC.

[Stefan Birnir Sverrisson]

Ok, thanks for your feedback.

Perhaps the higher current consumption has something to do with the PAN issue #35 "Consumes too much current when it is enabled and the STOP task is triggered", documented in the nRF51822-PAN v2.4 document. This anomaly is apparently fixed for third revision nRF51, see nRF51822-PAN v3.0. Your nRF51422 QFAC is third revision

The software version current consumption is higher because it uses the CPU (bit-bang) instead of the TWI hardware to implement the TWI protocol.

[michaeld]

That would probably be the problem. I'm investigating this because the production company placed the wrong variant an AA instead of an AC and are currently being fixed.

If I understand the revision matrix correctly the nrf51822-QFAC is only available as revision 3. So hopefully the problem will be solved when I get the PCB's back with the nRF51822 QFAC mounted. I will report back if so.

[michaeld]

This was indeed the problem, all problems are fixed when I upgrated to the nRF51822 QFAC REV3 (V3) BLE chip.