software TWI 1.3mA OFF MODE

RE: software TWI 1.3mA OFF MODE

tim — Sat, 20 Sep 2014 14:20:49 GMT

There were a number of challenges, but the problem was an interrupt pin was being pulled low. 1.38mA is the maximum driving current of the hmc.

RE: software TWI 1.3mA OFF MODE

Petter Myhre — Tue, 09 Sep 2014 06:19:35 GMT

Please edit your question to include the information. Read this if your are uncertain of how comments work.

RE: software TWI 1.3mA OFF MODE

tim — Mon, 08 Sep 2014 20:31:14 GMT

correction the system_off_mode_enter function works with soft device. After releasing the hfclk I do not request it again and the result is less power consumption while bonded.

The complete power consumption nrf51422 and mpu6500 in off state is about 20uA

RE: software TWI 1.3mA OFF MODE

tim — Mon, 08 Sep 2014 19:53:13 GMT

I have tried twi_hw_master.c and twi_sw_master.c with the following system off function.
It still does not reduce the power below 1.3mA called from within on_ble_evt

see

static void on_ble_evt(ble_evt_t * p_ble_evt)
    {
    //........
        case BLE_GAP_EVT_TIMEOUT:
            if (p_ble_evt->evt.gap_evt.params.timeout.src == BLE_GAP_TIMEOUT_SRC_ADVERTISEMENT)
            {
    // Go to system-off mode (this function will not return; wakeup will cause a reset)
                system_off_mode_enter();
            }
            break;
    //.....
    }
        
            void system_off_mode_enter(void)
            {
                uint32_t err_code;
                /*
                * OFF STATE
                */
                all_timers_stop();
           
                NRF_TWI1->ENABLE  = (TWI_ENABLE_ENABLE_Disabled << TWI_ENABLE_ENABLE_Pos);
                NRF_TWI1->POWER   = 0;
                sd_clock_hfclk_release();
                nrf_delay_ms(1000);
                err_code = sd_power_system_off();
                APP_ERROR_CHECK(err_code);
            }

RE: software TWI 1.3mA OFF MODE

tim — Fri, 05 Sep 2014 06:36:49 GMT

Yes, I perform a hard power reset, with the jtag disconnected before taking current measurements. I use the same testing process with and without the twi device attached.

When the twi device is attached the off state current is 1.3mA, combined the twi device itself consuming under 10uA (I verified this by hacking the hardware)
When the twi device is detached the off state current is under 5uA, approximate 3uA

RE: software TWI 1.3mA OFF MODE

Petter Myhre — Fri, 05 Sep 2014 05:21:04 GMT

Did you do a full reset (removing and re-applying the voltage to the chip) to disable the debug interface? Before doing the current measurement? Please see this question for more info.