Teensy 3.1 battery powered: correct pin used?

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deelaleo

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I have purchased a battery charger from Adafruit, to recharge the battery; and I would like to use it in my project. The item is this one: https://www.adafruit.com/products/1905

The idea would be to have the Teensy connected to this charger; so when the usb is connected the battery gets charged, and when I need to upload code, I hook up the USB to the Teensy and I do not need to remove the battery.

From what I understand, I can cut the trace to disconnect the power section coming in the USB cable, so it will just be used for data. But I am not sure how to wire the Teensy to that charger...I see the Vin, which accept up to 5V (and that charger has a 5V out, I believe, on the breakout pins, altho since it is coming from the battery, it will be about 4.3V); so the correct way to connect the Teensy would be to use the Vin pin and the GND on the opposite side ?

Then, if I use the 3.3V out on the Teensy, which GND should I use? The same one used to power the Teensy? the AGND? the GND on the pins on the other side of the usb connector (the one closed to Program and DAC pins).

I also see a 3.3V and a vBat pin, which I am not sure exactly what are they used for.

Could anyone guide me about what each of these ground and power pin does, so I use efficiently the Teensy and avoid to damage it? Thanks
 
If I understand your question correctly, you need to
1. Cut the VIN-VUSB trace on the underside of your Teensy.
2. Run a wire from VUSB to 5V on the Lipo board.
3. Run a wire from the BAT output on the LIPO board to VIN on the Teensy.
Presto, the Teensy will get anything from 3.6-4.3V on VIN, which the Vreg should be happy with.

GND would be used to connect the Lipo / charger on the return side.

AGND is used as a return for analog signal measurements.

3.3V is the output from the internal voltage regulator inside the Teensy. It can handle up to about 100mA.

VBAT allows you to provide a coin cell power source for the internal real time clock, whenever the 'main' power for the Teensy is turned off. If you don't use the RTC, don't bother with it.
 
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deelaleo said:
But I am not sure how to wire the Teensy to that charger...I see the Vin, which accept up to 5V (and that charger has a 5V out, I believe, on the breakout pins, altho since it is coming from the battery, it will be about 4.3V); so the correct way to connect the Teensy would be to use the Vin pin and the GND on the opposite side ?
Click to expand...

I'd first cut the VUSB-VIN pads apart on the bottom side of the Teensy 3.1.

Then I'd connect 5V to VUSB, and BAT to VIN, and GND to GND.

Do not use AGND for power.

I also see a 3.3V and a vBat pin, which I am not sure exactly what are they used for.
Click to expand...

It's meant for keeping the RTC (clock, date/time) running from a tiny coin cell. Of course, this only works if you've added a 32.768 kHz crystal.

That pin can't power the rest of the board. It's only for keeping the RTC running when the rest of the board is powered down.
 
Much appreciated Paul and Constantin; I have cut the pads apart and wired gnd to gnd of the battery and VIN to the positive of the battery, and it works fine.

while using the charger, I am connecting 5V from the charger to VUSB on the back of the Teensy; GND to GND (the one close to pin1), and BAT to VIN.

Now, when I need to connect the Teensy to program it; Can I just leave everything as is, or do I need to remove the battery from the charger? I assume that since the USB pad has been cut, It won't get the 5V from the USB cable, but will use the battery for power, so I shall be OK?
 
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