Posted on October 16, 2015 at 14:13Yes it is a datalogger it uses an external I2C HDC1008 Humidity and temperature sensor to collect the measurements and then stores them on a microSD card. Since I use the Standby mode the only place I can save data is on the RTC backup register. Now it works like this (after flashing in the program):
1) It turn on and checks if it has the time set (in the RTC registers)
2) if (yes to the above continue else inti_USART and wait for current time and stores in the RTC backup)
3) check if microSD card is present (one of the pins is grounded by the socket if the microSD card is inserted)
4) if (yes to the above continue else go to standby and start from the begining)
5) Turn on I2C set the sensor to measure Temp and Humidity, go to Stop mode (wait for the sensor to convert measurements (~6-7ms))
6) Wake up from stop mode get measurements, store them in the RTC register.
7) Go to standby mode.
Go to step 1)
The above repeats for 30 times after the RTC registers are full of measurements (30) then after the 6th step it goes here:
6.1) Init microSD card (I turn it on with a field transistor)
6.2) Get all info about the existing files and record it to the RTC registers, so it would only have to do it once. The info contains the name of the latest CSV file, how many lines are there in the file and etc)
6.2) opens the latest file moves cursor to line after the last recording.
6.3) Loads measurements from RTC to an array and counts back time to when they were taken.
6.4) Writes all data to microSD card and closes it (field transistor off).
6.5) Moves the RTC pointer back to the begining for measurement loading.
Go to step 1);
The steps 2), 4) and 6.2) are made only once to collect the data later on the device has it in the RTC registers.
As I mentioned I already have turn off the prefetch buffer and tried a few clock configurations but all in all I can't get it down lower than ~200-250uA. I am measuring the current connecting a small resistor in series and a lot of caps in parallel on the supply positive. It is an integrator and helps me to see the average power consumption.
