Here is my own designed SAM DEV BOARD its based on the ATSAMD21G18 32bit ARM Processor and uses a Buck Boost Converter which provides 2.5V min up to 12V max that means you can use  NiCd , NiMH or Lithium Cells to power this Board up. I recommend you to use two cells in parallel to have more mAh. This Board also includes I2C , Debugger and SPI headers plus 3.3V and 5V Connectors as well.

Core Processor ARM® Cortex®-M0+ Core Size 32-Bit Speed 48MHz Connectivity I²C, LINbus, SPI, UART/USART, USB Peripherals Brown-out Detect/Reset, DMA, I²S, POR, PWM, WDT Number of I/O 38 Program Memory Size 256KB (256K x 8) Program Memory Type FLASH EEPROM Size - RAM Size 32K x 8 Voltage - Supply (Vcc/Vdd) 1.62V ~ 3.6V Data Converters A/D 14x12b; D/A 1x10b Oscillator Type Internal Operating Temperature -40°C ~ 85°C (TA) 1x Cortex Debug Headers 1x I2C Headers 1x SPI Headers 5V supported

**update 1.5**

Put seperate Pins for the Power Ports 5V 3.3V and VIN
Arrange Components and routed new by Hand.
Changed Reset Pin Position to a appropriate place for shorter trace. 

**update 1.6**

Changed once again some traces and changed the size of the vias as well because JLCPCB supports only drill holes thats min 0.2mm.
And Arranged some Components and routed by hand again.

**update 1.7**
 
Make the Board slighty and fonts bigger to recognizing the Labels better.

**update 1.8**

 
changed the U1 TPS63061DSCT Buck Boost feedback trace position in front of Schottky Diode D1.

**update 2.0**

 
changed  H5 I2C header in 2x4 pinheader also H1 JTAG Port to 2x3 Pinheader.