The lobstar - An OSH, low-cost, breadboard-friendly Arduino-compatible clone

By -
There's a revolution underway in Computer Science education. The Raspberry Pi has generated a huge amount of energy and enthusiasm, but there's also a lot of interesting activity around the Arduino.

One great Arduino resource is the Shrimp, a low-cost compatible design aimed at educators and hobbyists with limited budgets.

Landing the Shrimp

You can find out more on the Shrimping It blog. It describes
'the Shrimp – a substitute for the Arduino Uno, which can be constructed for about a tenth of the price of the official board, shown here in stripboard and breadboard versions.'
Note the absence of a PCB version! That's deliberate: the idea is that you will lean more, and feel more of a sense of ownership, if you have constructed the shrimp from scratch.

That makes sense but I can see two situations where shrimp-catchers might prefer a PCB to work with.

  1. Some beginners starting out on their own might feel more confident building a PCB; an early win is important for building confidence.
  2. Old hands often want to put something Arduino-compatible at the heart of a prototype, and want a small and inexpensive system-on-a-board, ideally in a DIP format.

Enter the lobstar

The lobstar borrows unashamedly from the Shrimp's minimalist design; it has everything I want for prototyping, but no more. It has a header for In-system programming and a resonator to make the clock accurate enough for Serial comms, I2C and SPI. It plugs into a breadboard, and it has a reset button. And thanks to AVRISP, it has a bootloader.

No LEDs, no power regulator, no USB interface. I don't need them for what I want to do.

Fritzing it

The shrimp has a breadboard version so it was easy to capture and modify the design in Fritzing. I decided to use it as a pilot project while learning how to use Fritzing to generate a PCB design.

Of course, as always happens, I made a couple of mistakes.

Version 0.1 swapped ground and the 5v power on the FTDI header. Amazingly, nothing was damaged, and I was able to program it using a kludgy but effective stripboard.
lobstar v 0.2
Version 0.2 (the one I got made by ragworm) was a significant redesign and I managed to introduce an extra trace which I had to cut through with a craft knife.

Version 0.2.1 is currently on its way back from oshpark. (I used the lobstar as a way of trying out several different PCB fab shops, and will post about my experiences when the next lot of boards arrive.) There's a picture of version 0.2 in yesterday's post.

Even though v 0.2.1 is still untested I have open-sourced the design. You can follow its evolution on Github. oshpark generated a preview to show what the board will look like, shown below.
oshpark preview
The earlier versions are working well (after suitable surgery) and do just what I hoped.

Conclusion


If you want to learn or teach about Arduino on a budget, a shrimping workshop sounds like a great idea. If  you want a source of easy-to-make, easy-to-use, inexpensive Arduino-compatible clones, you can use Fritzing to create your own custom PCB. You could even make use of the lobstar design!    

Comments

Post a Comment

Popular posts from this blog

Controlling a Raspberry Pi Pico remotely using PySerial

By -
Image
Update : I'm using thie code below in another project, and found that I had not correctly fixed the reported bug. The new version passes automated tests, and I am pretty sure it works OK. I have changed the name of the class to Talker  since it can both send and receive information. Apologies to all concerned for the bug! Introduction You can use a Raspberry Pi Pico as a powerful peripheral to a host - a Raspberry Pi, a Jetson Nano, a laptop or workstation. In this article you'll see how to interact with a Pico running MicroPython or CircuitPython by writing some Python code that runs on the host. The software is easy to use. It enables you to send a Python statement to the Pico and read the results. The statement can be any valid MicroPython code. Setting up the host and the Pico For this article I've used a Raspberry Pi as the host, but any computer running Windows, Linux or Mac OS will do so long as it has Python 3.5 or later installed. In particular, you can use this t...
Read more

Five steps to connect Jetson Nano and Arduino

By -
Image
Yesterday's post showed how to link a micro:bit to the Jetson Nano. One of the members of the (unofficial) NVIDIA Jetson Nano group on Facebook asked about connecting an Arduino to the Jetson. Here's a simple recipe for getting data from the Arduino to the Jetson Nano. It should work on all the Jetson models, not just the Nano, but I only have Nanos to hand. On request, I've added a recipe at the end of this post which sends data from the Jetson Nano to the Arduino; it turns the default LED on the Arduino on or off. The recipe for sending data from the Arduino to the Jetson has just 5 stages: Program the Arduino. (I used the ASCIITable example). Connect the Arduino to the Jetson using a USB connector Install pyserial on the Jetson Download a three-line Python script Run the script.   Programming the Arduino I used an Arduino Uno, and checked it on a verteran Duemilanove (above), but any Arduino should work. You'll need to do this step usi...
Read more

Raspberry Pi Pico project 2 - MCP3008

By -
Image
This post show you how to drive the MCP3008 8-channel ADC using a Raspberry Pi Pico. I'll start with a personally embarrassing and annoyingly relevant story. I'll also tell you about a minor 'gotcha' when using SPI on the Pico, and how you can avoid it. Finally, I've include the code and fritzing diagram I used to test the interface. First, the story. Back in 2012, when the Raspberry Pi was fresh and new, I was running a startup called Quick2Wire.  We made add-on boards for the Pi. Just before Christmas we sent out our first batch of boards to a small army of beta-testers. The beta boards didn't work. Somehow a single trace on the pcb had got deleted and one of the GPIO pins was isolated. The boards were still usable and it wasn't too hard to solder in a jumper wire to replace the missing trace, but it was very embarrassing. It wasn't just that we'd shipped boards with a defect. The really annoying thing was that I'd set up an  automated loop-bac...
Read more