On Mon, Feb 20, 2017 at 5:39 AM, Internet <internet@devpi.de> wrote:
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.
yeahhh i was going to use a txs0104, but then decided to remove it from the board... i'll put it back. there are a couple of other signals (the IRQs) that need to be level-shifted up as well
*sigh* a 1.8v voltage regulator just for a few micro-amps... :)
Julius LehmannOn Feb 19, 2017, at 22:56, Luke Kenneth Casson Leighton <lkcl@lkcl.net> 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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