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  • Author Author: genebren
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Mr. Machine gets an upgrade - New boards, but not enough time

genebren

In my prior blogs (Mr. Machine gets an upgrade - working on the pieces. , Mr. Machine gets an upgrade - new internals, motors installed and new PCBs and Mr. Machine gets an upgrade - time is running down ) I walked through Mr. Machine's history and some of my updates.  This time I will wrap up what I can as the project14 deadline closes.

 

I was very concerned as time ran down and my boards had not yet arrived.  Late Saturday afternoon (12/12), the boards finally showed up.  I jumped right in, finishing a few design details (schematic and BOM) and moved on to assembly.  Here are some shots of the finished boards:

 

imageimageimage

 

Clockwise from the upper left hand corner, are the Power Pack, Motor Driver and Controller boards.   During the finalization of the schematics and BOM, I noticed a few errors on the controller board.  First, I noticed that I had mapped one of the pins incorrectly.  The Midi player function uses an timer compare output that is available on Pin3, but I somehow connected Pin2 to the low pass filter and on to the audio amplifier.  The other error was due to a bad assumption that I made concerning the hardware support of the I2C port on the ATTINY85.  Device is basically a simple serial port and requires a fair amount of bit banging to actual function as an I2C port.  With the high rate of sampling needed for the four-voice PWM tone generation of the Midi player, it would be very difficult to get any reliable/repeatable timing on the I2C bus.  I decided to isolate the ATTINY85 part from the I2C bus (mainly used to communicate between the three boards.  Instead, I routed the two signals from the ATTINY85 to two unused pins on the ATMEGA328PB (to be used as a start/stop control and a status line.

 

Here is the updated schematics and BOM for each of the boards:

 

First the Controller Board.

imageimage

 

Motor Driver Board.

imageimage

 

Power Pack Board.

 

imageimage

 

The overall connection diagram is as follows:

image

 

I have started writing/porting the firmware from the WalkyII project, but I have not gotten far enough through the process to document the firmware at this time.  I fully intend to complete this project and I will continue to blog on my progress/results.  All in all this was a fun project undertaking.  I learned a valuable lesson from my deadlines issues with the printed circuit board, which is, complete all of your long lead time orders earlier in the project time line.  I spent a huge amount of time designing and printing all of the plastic parts and I left the final electronic design details and ordering towards the end of the project.  This is a mistake I hope not to repeat in the future.

 

Thanks for following along on this journey with me.  I don't know about you, but for me, this has been a lot of fun!

  • in reply to ralphjy

    Thanks Ralph!  A labor of love.  I am digging in to the firmware now.  I have the Midi played running on the new controller board and I am digging into the remaining controller functions.  I hope to have this all running before my grandchildren visit again.  I will continue to post as I make progress.

     

    Thanks again.

  • Gene,

     

    Great project!  Quite a lot of complexity for a Project14 build (or maybe that should be effort).  I think you did a lot in the short timeframe.  Glad that you're having fun with it image.   Can't wait to see it working.

     

    Ralph

  • in reply to dubbie

    Thanks Dubbie.  The PCB making process is really getting a lot easier with many free tool sets (Eagle has a free, limited version) and many online vendors.  At the lowest levels it can be very 'lego like', just a series of building blocks.  But, as the complexity increases it can require a fair amount of electronics knowledge.  Using a PCB as a interconnection media (sort of like a motherboard), sure makes prototype builds easier than soldering a bunch of wires in place.

     

    I am really excited to get this guy up and running.  I am going to keep working on this project, as my Grandkids are quite interested in this project.

  • Gene,

     

    The PCBs look really nice. One day I hope to be able to do the same. Maybe I will make it one of my jobs for New Year. I'm also looking forward to seeing the completed robot up and running (or probably walking very slowly)

     

    Dubbie