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bq27621-G1 System-Side Fuel Gauge - default values and exit shutdown mode

asher khagbi
Intellectual 420 points

Hi all

I have a fuel gauge connected to CC2460

When I wake up from unexpected reset, even after I disconnected the battery, the FG set/get is not working

But, when I do what needed to exit shutdown mode (. If the device is in shutdown mode, then toggling GPOUT will make the gauge exit shutdown)- everything is OK

spec: http://www.ti.com/lit/ds/symlink/bq27621-g1.pdf  

my questions are:

1. in the spec: after reset it back to default values. what are the defualts? especially the shutdown mode

2. if it was in shutdown mode before reset occors, after disconnecting the battery,  is the FG remember the shutdown mode that was before?

3. Is there any problem to toggle GPOUT  in order to make the gauge exit shutdown, even if it is NOT in shutdown mode?

 

Thanks ahead to all who answer

  • 0
    TI__Guru 61536 points

    1. the default values are listed in the TRM (www.ti.com/.../sluuad4c.pdf), 6.2.
    2. if the gauge is in shutdown mode it is essentially powered off (the LDO is off). Toggling the GPIO will turn on the LDO and start up the gauge. This is not necessary if you first connect the battery, only after you issue a shutdown command.
    3. it is not a problem as long as you do not drive the pin to a logic high level. It is an open drain pin so you'll have to generate the logic high with a pull-up resistor (just like you do with the SCL and SDA lines on the I2C interface)

  • 0 in reply to Dominik Hartl11
    Intellectual 420 points
    Thanks a lot for the answer, but
    1. in 6.2 there is no default, but 6.2 Data Types Summary!?!

    2. that is exactely what I thought! but I see situation that set/get do NOT work, until the toggling of the GPIO, than, all works, any idea (after reconnect)???
    IMPORTANT NOTE: this is happenning only when the tag connected to the programmer, and I burn it again, so reset occurs,NOT REALY PYSICALLY DISCONNECT, but when I work with real battery and I disconnect it, shortcut the battery nodes, and connect it - all fine!!!

    3. thanks, my dought is because it is OUT pin, so maybe it can create collisions
  • 0 in reply to asher khagbi
    TI__Guru 61536 points
    1: 6.2 and 6.3 show the data types and data memory summary. Each subclass has min/max/default. The default values are loaded after a gauge reset.

    2: I don't have this problem with my 621 EVM. It works immediately after I connect a battery. What do you mean with "tag connected to the programmer". Is the tag the same design as the EVM from a gauge point of view? What programmer do you use?

    3: It's an open drain IO so it can drive a 0 (FET to GND) but not a 1 (relies on an external pull-up resistor). If the gauge is configured to use the GPOUT pin for an interrupt and you drive a logic 1 externally (not via a pull-up resistor but with a FET from a push-pull output on your host uC) then you will create a contention if the gauge drives a logic 0 (=connect to GND).
  • 0 in reply to Dominik Hartl11
    Intellectual 420 points
    Thanks

    I have capacitors in the chip, I see that the FG is not working correctly if there is some power around, like in the capacitors (like the Accelerometer)
    The solution I found, is to make a shortcut to the tag, this step discharge all the capacitors, and than the FG is working properly!

    Another solution, is to start toggling the GPOUT pin, in the beginning of the initialization - this can do the job as well