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Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
@aerialist_user6911
Hi,
I love Espruino board and I'd like to embed Espruino together with Lithium Polymer battery into a case, with one opening for uUSB.
I'd like to add battery charger circuit so that battery would be charged when uUSB on Espruino is connected to PC.
Does anyone have recommendation which charger IC to use and how to connect?
Reading Espruino document at
http://www.espruino.com/EspruinoBoard
http://www.espruino.com/Battery
I understood that Espruino board does not have charging IC on board. "An unpopulated resistor that can trickle-charge a battery when fitted" sounds tempting but I feel better not to take risk after reading this tutorial.
https://learn.adafruit.com/li-ion-and-lipoly-batteries?view=all
Searching around, it seems easiest to put off-the-shelf charger board into the case.
https://www.sparkfun.com/products/10401
Or MAX1555 charger IC seems simple enough to put on SMD proto area.
https://www.sparkfun.com/products/674
Now my question is: how to wire the charger IC between the battery and Espruino, and how to get uUSB 5v supply to the charger IC.
Checking the schematics of this product
https://www.sparkfun.com/products/12711
https://cdn.sparkfun.com/datasheets/Prototyping/USB_LiPolyCharger_SingleCell21.pdf
It looks like I can just connect the battery and Espruino's BAT_IN in parallel to MAX1555's BAT pin. I guess it has to be BAT_IN rather than VBAT. (am I right?)
I think I'd access BAT_IN by soldering a wire to JST PHR-2 2 Pin.
Now how should I get power supply to the charger IC? MAX1555 takes 3.7v to 6v so Espruino's 3.3v pin is just under. Mmm, reading Espruino schematics again, VBAT seems to become uUSB's power when it is plugged-in. Then it's easy.
As the conclusion, I think all I need is:
Plugging-in uUSB and battery together is ok thanks for Gordon to implement MOSFET-P-0440210P1 switch. And it also enabled easy access to get uUSB's 5v supply to charger IC. Cool.
I hope someone could confirm above is right before I give it a try and blow up my precious Espruino board...
And I'd appreciate any extra advice ;-)