For all following suggestions you need a 1.8v power supply (buck converter). 
First, you could disable internal pullups on the stm and remove all pullups on 
PCB2 for the signals from the battery ic. Because the signals are probably all 
opendrain you just need to pullup the signals on pcb3 to 1.8v; either the stm 
or the battery ic can pull the lines low to "activate" them. The stm should 
recognize 1.8v as high ...

Second, you could add a txs0104 or two txs0102 (probably cheaper, you can get 
those from aliexpress) for level shifting. They have internal pullups, so you 
can remove the other pullup resistors as well.

Julius Lehmann

On Feb 19, 2017, 22:56, at 22:56, Luke Kenneth Casson Leighton <[email protected]> 
wrote:
>btw annoyinly the BQ27542 is designed for 1.8v operation, and the
>STM32F072
>it's connected to operates its GPIO at 3.3v.  suggestions on how to
>deal
>with this appreciated.
>
>l.
>
>
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