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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:


PCB assembly - top viewPCB assembly - bottom viewController Board Rework


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.

Revised controller boardController Board BOM


Motor Driver Board.

Revised Motor Driver boardmotor driver BOM


Power Pack Board.


Revised Power Pack SchematicPower pack BOM


The overall connection diagram is as follows:

Connection details


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!