We are planning to use Ruuvi tags without using the accellerometer or the pressure/temperature/humidity sensors. We will be reprogramming the nRF52x host to use very low power and we do not want either sensor drawing much power from the battery. I can see from their datasheets that both sensors use very little power when they are “powered down” or in a “sleep” mode. So, we will just need to ensure that both sensors are in a low-power state. Are each of the sensors in a low-power state by default when they are powered up or do we need to exercise each of their SPI interfaces to put them into a low-power state? If we need to put each sensor into a low-power state, please advise if there is sample code that supports this function.
Are you sure? In looking at the schematic for B6, I see no gpio control of these modules, just the SPI interface and a couple interrupts coming from the accelerometer to the Nordic part.
Module power control via gpio would be great for a future rev.
If each modules default state at power up is a “low-power” state, then no change is required. If not, the SPI interface to each module will have to be used to put each module into this state.
By GPIOs I meant all the lines connected between sensors and nRF52. Like you said, there are SPI bus lines and interrupt lines which all should be configured to known states (which will not draw power) after reset.
If you’re going to buy in bulk, contact sales@ruuvi.com for a quote of RuuviTags without the sensors. That will save you a few microamps of stand-by current as well as a bit of money.