[Arm-netbook] Laptop PCB schematics

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

On Mon, Feb 20, 2017 at 5:39 AM, Internet <internet at 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 Lehmann
> On Feb 19, 2017, at 22:56, Luke Kenneth Casson Leighton <lkcl at 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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