Wemos SAMD21 M0 Arduino M0 Compatible Board

An Arduino M0 compatible board called Wemos SAMD21 M0 is available from several online shops such as Banggood, AliExpress and Amazon, and also appears from several sellers on eBay. What appears to be the same board is also marketed as RobotDyn SAMD21M0. This blog post provides more information on the board.

An image of the Wemos SAMD21 M0 is shown below. As can be seen in the image, the Wemos logo appears on the board near the SAMD21G18A microcontroller chip. This board is not an exact copy or clone of the Arduino M0, but has a few differences such as the extra TXD and RXD pins found at the end of the board.

WeMos SAMD21 M0 Arduino M0 Compatible

WeMos SAMD21 M0 Arduino M0 Compatible

Wemos SAMD21 M0 Board Logo

Apparently this board is not actually made by the Wemos company, but the board is silk-screened with the Wemos logo. This has been mentioned on the Arduino forum in a few places. Here are a couple of examples:

Arduino forum message mentioning that the Wemos board does not appear on the official Wemos website.

An Arduino forum user mentions that Wemos does not admit the existence of this board.

Arduino M0 Compatible

The Wemos SAMD21 M0 board is compatible with the Arduino M0 which was originally from arduino.org when arduino.org and arduino.cc were having their fight. Now that the two companies have finished fighting and merged back together, the Arduino M0 board is listed on the arduino.cc website.

Circuit Diagram

I have not found a circuit diagram for the Wemos SAMD21 M0 after extensive searching. As the board is compatible with the Arduino M0, the Arduino M0 information page will be useful. A circuit diagram or schematic for the Arduino M0 can be found under the DOCUMENTATION tab on this page.

Wrong Information

On many of the sellers web pages for the Wemos SAMD21 M0, there is incorrect information about the board that describes it as an Arduino Zero or Arduino M0 Pro. The information also mentions that it has Atmel’s embedded debugger (EDBG) on the board – this is not true. Only the Genuino Zero and Arduino M0 Pro have the EDBG.

Older Boards

Some users of earlier boards complained about the power LED being too bright. There were also complaints about the board not working with the Arduino IDE. This has changed with the newer boards. I have not had these problems with boards ordered in 2018.

Hardware Differences

Although the Wemos SAMD21 M0 board is compatible with the Arduino M0, it is not a clone or exact copy of the Arduino M0, but rather a variant of it.

Two extra serial port pins can be seen at the end of the board. These pins are labeled TXD and RXD. The power supply looks different between the boards and some of the components such as LEDs are in slightly different locations on the boards.

Wemos SAMD21 M0 Quick Start Tutorial

A Wemos SAMD21 M0 quick start tutorial can be found on the Starting Electronics website. This tutorial shows how to install the programming tools to program the Arduino M0 and compatible boards in the Arduino IDE. It shows how to blink the on-board LED as a quick test to see that the board is working and then shows how to use the serial ports to communicate with the Arduino IDE Serial Monitor.

Go to the Wemos SAMD21 M0 tutorial →

Unpacking a Atmel SAM4N Xplained Pro Evaluation Board

The Atmel SAM4N Xplained Pro evaluation board contains a ATSAM4N16C microcontroller. The board itself is rather basic with only one user programmable LED and one user programmable push-button switch (the second switch is a reset switch). Pins of the microcontroller are available on headers on the board.

An on-board Embedded Debugger is included on the board, so that no external tools are required to program or debug the ATSAM4N16C.

The video below shows the evaluation board being unpacked.

Some features of the ATSAM4N16C microcontroller are:

  • ARM Cortex-M4 that can run up to 100MHz
  • 3 USARTs and 4 UARTS
  • Real Time Clock (RTC) with calendar and alarm features
  • 10 bit ADC and DAC
  • 1Mb Flash memory
  • 80kb SRAM
  • The usual SPI, TWI, timers, PWM, etc.

The ATSAM4N16C does not contain any USB ports, Ethernet or external bus.

Resources from Atmel

Large PLC – Open Source Hardware

The large brick-type open source PLC has 22 digital inputs, 6 analog inputs and 16 transistor outputs. It also features a SD card socket, 2 RS-232 ports, 1 RS-485 port, 1 USB device port and a JTAG port for programming and debugging.

Large Open Source PLC

Large Open Source PLC

All the source files including circuit diagrams for building the large open source PLC are available for download at the above link.

Small PLC – Open Source Hardware Project

This small brick-type PLC open source hardware project is based on an ARM7 microcontroller from Atmel. The PLC has 10 digital inputs, 8 digital outputs, 4 analog inputs, a real time clock, RS232 port, RS485 port, USB port and JTAG port.

More information and circuit diagrams are available at the above link.

Small Open Source PLC

Small Open Source PLC