<div dir="ltr"><br><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature">---<br>crowd-funded eco-conscious hardware: <a href="https://www.crowdsupply.com/eoma68" target="_blank">https://www.crowdsupply.com/eoma68</a><br></div></div>
<br><div class="gmail_quote">On Mon, Feb 20, 2017 at 5:39 AM, Internet <span dir="ltr"><<a href="mailto:internet@devpi.de" target="_blank">internet@devpi.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="auto">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 ...<br><br></div>
<div dir="auto">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.<br></div></div></blockquote><div><br></div><div> 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</div><div><br></div><div> *sigh* a 1.8v voltage regulator just for a few micro-amps... :)</div><div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div dir="auto"><br></div>
<div dir="auto">Julius Lehmann</div>
<div class="gmail_quote"><span class="">On Feb 19, 2017, at 22:56, Luke Kenneth Casson Leighton <<a href="mailto:lkcl@lkcl.net" target="_blank">lkcl@lkcl.net</a>> wrote:</span><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span class="">
<div dir="ltr"><div class="gmail_extra">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.</div><div class="gmail_extra"><br></div><div class="gmail_extra">l.</div></div>
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