I2C links Arduino and Beagleboard

By -
I want to revise the design of my I2C-based LCD board. The old design works, but it's not reliable and it puts a lot of traffic on the I2C bus. I'd prefer something that created less traffic and placed fewer demands on the host.

I2C is a great protocol for connecting sensors to micro-computers, but you can also use it to link two  computers together.

The solution that I'm looking at will use an Atmel 8-bit AVR  processor to drive the LCD and act as an IC2 slave. That way the host computer needs to send just two bytes down the wire to write a character. The current design sends three or four times that many.

I'm going to develop the solution in small steps:
  1. Get the BeagleBoard talking to an Arduino over I2C with BB as master and Arduino as slave.
  2. Connect the Arduino to the LCD.
  3. Add LCD driver code to the Arduino sketch, and control it using I2C
  4. Put an ATMega8 in a DT104 board from Dontronics. I have several of each spare.
  5. Program an arduino bootloader into the ATMega8.
  6. Upload the I2C-LCD sketch to the ATMega8.
  7. Build a simple stripboard base for the LCD and the motherboard and connect them up.
Voilà!

Step one is done.

There's a handy I2C slave sketch among the Arduino examples, and a good tutorial showing how to connect two Arduinos on the main website. I've programmed the Arduino slave to sit on I2C address 4.

It's safe to connect the Arduino and the BB because tincantools' Trainer-xM board shifts the Beagle's 1.8v I2C signals to the 5v required by the Arduino and vice versa.

I found a useful blog post about using the Beagleboard I2c tools to drive another kind of device; it's easy to adapt the given command to talk to the Arduino.  When I type

i2cwrite 2 4 67
on the  Beagleboard, it sends a byte value of 67 on bus 2 to the device with I2C address 4 and the character 'C' (ascii decimal 67) is received by the Arduino.

Connecting the Arduino and the LCD

I expect that Step 2 will be the most time-consuming; patching together an Arduino an LDC is fiddly, but I've done it before and there are very clear instructions from Oomlout for the LCD that they supply.

Once that's done the rest should be fairly straightforward.

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