arduino due + li-ion battery + usb charging

hi everyone, i'm working on a project i prototyped with Arduino DUE. i'd like to create my own board and i want to use it with a lithium battery. i read a lot of threads about this but nothing about Arduinon DUE. For example: Can i use Arduino FIO scheme in this case? where do i have to connect the supply for the SAM3x?

where do i have to connect the supply for the SAM3x?

For backup or normal running?

For normal the VDDIN pin is the power supply, but there are a lot of other pins that have to be connected to VDDOUT and each other and other pins through chokes etc. It's not as simple as an AVR.

For backup connect to VDDBU.

Have a look at the Due schematics.


When fully charged, li-ion batteries have a voltage close to 4.2V, so I would recommend to connect it to the 3.3V of the due. Also keep in mind that the due does not have a charging circuit, so be careful when connecting the battery and the usb at the same time (it might explode)

The fio is different because it has an integrated charging circuit, to protect the battery and the board.

i copied the charging circuit of the FIO and connected the output voltage of the battery (regulated to 3V3 as in FIO) to the 3V3 of Arduino DUE in the schematic. is it ok?

i have another couple of question:
1.which connector do i need to bootload SAM3X and AtMegA16U2?
2.i don’t need USBOTG. can i take out from the schematic the part about the USBOTG then?

  1. Not sure what you mean here, if you want to connect USB to the 16U2 then any of the standard USB A, B, miniB or microB sockets.

  2. If you don't plan to use the USB port on the SAM you don't need to implement any of that circuitry AFAIK.


thanks rob. my english maybe is too bad, i hope you can understand what i mean about question 1: the prototyping stage of my project is ended. everything works fine. now i want to create my own board. thus i have to print my pcb in which there are both SAM3X and ATMEGA16U2. i read SAM3X comes out from ATMEL with ROM flashed yet.

what about the ATMEGA16U2? i need to flash it, right? if the answer is yes, how do i accomplish this task?

i read SAM3X comes out from ATMEL with ROM flashed yet.

Yes the SAM has UART and USB bootloaders hardwired in ROM.

what about the ATMEGA16U2? i need to flash it, right?

Correct. You would provide a method to program via the SPI port.

If it's a one-off programming job (ie just the bootloader) then put 6 pads somewhere on the board that allow the connection of an ISP cable somehow. Some methods I know of are...

If you have the space add a standard 2x3 header footprint but offset the middle two holes a little bit so the header is an interference fit and will stay there by itself while programming.

Another way is to have two rows of pads on the edge of the board, 3 pads on each side. This allows you to slide a header onto the board for programming (you will have to bend the header pins a little to get a firm fit).

And another way is to have a very small footprint of 6 pads and use "pogo pins" to make the connection for programming.

There is also a special connector designed to clip into a matching footprint on the board, unfortunately I can't find the details right now.

And finally you can program the chip in a ZIF socket before soldering it in, this might be OK for a mass-produce item but it means you can never change the program so not a great idea normally I think.


Another option might be to use the newer LiFePO4 which has a working voltage of 2.9-3.3V and charging up to 3.6V.
LiFePO4 is designed to be intrinsically safe and can’t blow up like LiIon can do(see Boeing Dreamliner Battery Pack issues)
There is also an interesting solar Powered LED Flood Lights with solar panel and charger and two LiFePO4 batteries
available at my local for $30.
Portfolio 3-Pack Black Solar-Powered LED Flood Lights Model #: SS13P-P2-BK-PK3
In the sealed solar module this has two removable LiFePO4 each 1AHr batteries.
I’ve attached a graph of the battery voltage using just one LiFePO4/1AHr over about 3days of solar charging, and then at night the LED Floodlight turns on and when the battery is discharged it Low Voltage Disconnects. When the sun comes up it charges the battery till it is full and then jumps from 3.35V to 3.65V