NET3001 Teaching Board

MTS2: microcontroller training system

current status
teaching opportunities
notes on the hardware design


For the last few years I have been teaching a course in real time programming. The 3 month course consists of
The students write code on an embedded microprocessor. Previous versions of this course use the HC12 and the MSP430.

I wanted to create a course where the students could bring the development system home, and work with their own PC. That meant:

To demonstrate the various aspects of the course, the board must have:

Current status

I have designed this
Here's a photo.



I wanted the CPU to be easy to teach, and I wanted to move up to 32 bit. That points to the ARM processors, and the Cortex in particular, which are at a great price-point.


The CPU needs to allow easy download and single stepping, as well as the ability to view registers and control I/O ports. Again, the Cortex processors do that well.


Almost all the chips on the board run at 3V or 5V, so a USB cable can provide all the power. The backlight on the LCD requires +7V, and the RS232 requires +/-7V; the MAX232 chip can generate both of these.
In order to run the servo motors, however, we need a lot more current, so the board has a LiPo battery 150mAH which provides the surge current required by the servo motor.


The students in the course are also learning about network protocols in their other courses. So this board has a 2.4GHz radio transceiver. This unit is low cost, only chews about 10mA when it's running, and has a full packet fifo and MAC features (preamble, header and CRC assembly). The students can either use it at this level, or introduce a link-level protocol. The packet payload can be up to about 25 bytes, or even more if the CRC & address fields are reduced.


There are three motors on board. The DC motor is driven by two PWM pins, which allows us to speed it up and slow it down, and even reverse it.

The stepper motor is a 4 pin unipolar drive, so the drive sequences are

Both should be fairly easy to teach.

The servo motor requires 1.5msec pulses every 20msec. Teaching this will be a challenge, and we may not get to it in the basic course.


Provisional: CDN$40 for parts. Labor will probably be me-&-free. Many of the parts are coming from surplus houses, HongKong eBay and Digikey.

Teaching Opportunities

Some assignments which I am considering
There are several opportunities to teach physical feedback:

Hardware design notes

  1. nRF24L01 modules
  2. There are two designs for this module: an 8 pin and a 10 pin. My board is designed for the 8 pin version. But I had a hard time getting it to work; it turns out that the module is sensitive to glitches on the rails, and my board wasn't well designed to feed power to the module. A 10uF cap across the rails at the module fixed it. I was accidentally sent 20 modules of the 10 pin variety. Fortunately, 7 of the 8 pins line up, so the mod was trivial to get the 10 pin versions to fit. This module is not as sensitive to glitches on the rail; I assume there is on-module filtering.
  3. Servo motors
  4. I ordered the 9g motors that are designed for model helicopters. Of course, the samples I got consumed 3mA when idle and 60 mA when active. But the production quantity consumed 6mA when idle, and peaks of 300mA when active. This forced me to add a LiPo battery as a mod, in order to supply enough current to the motor. In hindsight, I should have dropped the motor from the project.
  5. Accelerometer
  6. I'm using the MMA8453. Be warned that this chip does not neccessarily power up in a clean state; you must perform a software reset before using it.