MSP430 and BOOSTXL power consumption

[Kris2475 0]

Hi,

I’m trying to get my MSP-EXP430FR5969 (or preferably MSP-EXP430F5529) to work with BOOSTXL-SHARP128 at a few uA when it is not selected or being written to, i.e. when it’s idle. My MSP430s consume only a fraction of a uA in lowest power mode, but as soon as I add myScreen.begin() to setup(), it all goes crazy.

In my sketch (below), I have set all ports as outputs to ensure there are no floating inputs. This reduces current consumption from several hundred uA to ~160 uA. I then connected my BOOSTXL-SHARP128 to my MSP-EXP430FR5969 via jumper wires to LCD_DISP, LCD_CD, SPI_CLK, SPI_MOSI, and gnd. This is enough to enable me to write to the display (ignore the green LED - I disabled this later). I tied MISO to gnd, since it is an input and isn’t used – this reduces the current consumption further to ~140 uA. I’m guessing P1_7 was re-initialised somewhere in one of the function calls to be an input, even though I initialised it as an output in setup()?  Interestingly, my code doesn’t write anything to the display when the module is plugged directly onto the MSP430, and the current consumption also shoots up to a couple of mA!

Am I correct in thinking that even after I have initialised the ports as outputs (using PnDIR) and set the outputs to HIGH (using PnOUT), sketch functions can still use those ports as outputs, i.e. the output ports can still be switched between HIGH and LOW by code in loop()?

I was expecting to get the current consumption (measured on J9) down to just a few microamps. Is there anything I’m missing?

Thanks in advance for your help (and for responses to previous questions!)

Kris

[Rei Vilo 695]

Two pointers:

• Check the schematics of the BOOSTXL-SHARP128,
• Mistrust the readings of your DMM as it may suffer from the impact of burden voltage.

About burden voltage, read for example http://eevblog.com/files/uCurrentArticle.pdf and http://literature.cdn.keysight.com/litweb/pdf/5992-0418EN.pdf)  

[Kris2475 0]

Thanks for your reply. Regarding burden voltage, I have tried switching to mA range and read 0.14 mA, so I don't think that's the problem. I read the same current (140 uA or 0.14 mA, depending on DMM range) when the BOOSTXL-SHARP128 is not physically connected to the Launchpad. The current goes down to sub-uA when I comment out all of the myScreen functions.

[Kris2475 0]

I've commented out all of the display stuff and disconnected the BOOSTXL-SHARP128. I'm not sure why it was drawing so much current with the BOOSTXL and myScreen functions?