ST1000 embedded TinyPilot - Projectlog & Questions

[seandepagnier]

After reading a lot about this great project and gaining some experience with Raspberry last summer we decided it was time for the next step. We had an old and broken ST1000 lying around, so converting that to PyPilot seems to be a nice project. Last weeks i have been reading and researching a lot. Deciphered some code and sketches, etc. Also made the first decisions toward the architecture I am gonna use. I would like to make a standalone pilot, so will embed al hardware in the ST1000's casing. After a lot of puzzling i think that i have puzzled out most of the connections. Resulting in this drawing:


Can someone say something about this sketch? Did I make wrong assumptions?

Not sure about the shunt wiring or the extra uC, what is it for?

Still wondering how to connect the Arduino and Pi. They share the same powersource, so in theory can be directly connected. That would make USB the easiest solution, cause you don't have problems with the 3.3V vs 5V architecture. But having an opti-isolated I2C-bus seems to be nice for future additions. Especially a remote display, which I am planning to make in the future. Can anybody share how they have made an isolated I2C connection between Pi and Arduino?

I opto isolate the uart not i2c. It is much simpler because each wire goes in one direction.

Second point of interest is the Motorcontroller. A SimonK based controller seems to be the easiest solution. But they seem to be not so much up-to-the-job as their specs say. So I will probably need a 30A version for the little Mabuchi motor which maximally draws around 10A. Because I still have to manufacture some kind of print to accomodate all the stuff, maybe it's easier and more reliable to put an H-bridge on that print then? Can anybody share their H-bridge designs?

Yes, I recommend at least 20A, or 30A if they are going to run efficiently and reliable if the motor draws normally a few amps.

Eventually, yes I changed to just put an H bridge. It is not really easier because a lot more parts to assemble, but no need to program multiple uC and also much lower idle current, and even better mosfets for more efficiency.

I hope to post the schematic I"m using soon when I update my site.

As you can see I have added a 6'th button. That's because the ST1000 has 6 buttons. Still deciding about

I recommend you don't wire the buttons to gnd, but to a 1k resistor to ground. That way if the program accidentally drives them when a button is pressed there is never a short.

The wire for the 6th button is already used by the lcd, so I would be careful of this. There are many more gpio available after 26. I intend to use these for more buttons in the future.

What are your 6 buttons, what do you expect the 6th button to do?

Do you have a plan for mounting the display so it can be read?

functionality of these buttons. The display is another topic, I will start with the Nokia one because that's plug-and-play. But am hoping to use a display with the same size as the original display in the future. Probably a small O-led screen because they have good readability at small sizes.

Let me know if you find a good one. the oled I think require a lot of power to be readable in sunlight.

Up next - in a few days - BOM and some pictures / practical sketches.

Hoping to have learned more about Motorcontrol, I2C-isolation and the faults in my sketches by then 

Thanks a lot guys!