myRobot re-visited

Got back to my favourite project yesterday. It’s been a difficult Xmas period, our cat got sick about a week before and we’ve been doing vets, and stuff, during most of it. Little chap seems to be on the mend, despite a fantastic ability to avoid any kind of tablet at all cost. The number of “experienced veterinary” types around here with scratches and scars will probably set some kind of record.

My first attempt at this turned out to be a bit of an abomination. I had tried to “add” lots of “stuff” – like temperature sensing in the motor compartment and voltage monitoring. All very interesting but not fundamental to what I was originally trying to do. I had problems with the last motor board (or boards to be more honest) but that’s not surprising given what I was trying to cram in to a tiny space.

That’s enough words, here’s the mess I made before…

IMG_20121028_202012

IMG_20121029_160046

IMG_20121030_143042That really was all too tight to fit in there. I had random shorts (probably because of several cock ups caused by last minute “wouldn’t it be good to add this too” stupidity on the MCU board). It just didn’t work and it was a real pain in the arse to work with.

Have left it alone for a while to let it all sink in and try to learn something from it. Bottom line? Less is more.

The new build has been stripped down to essentials.IMG_20130104_163311

That’s about it – minus the wires on the main board from the MCU to the motor controller and some male/female headers to connect stuff.

The lower part of the ATMega328 is utilised connecting to the lower part of the motor driver (these motors are a bit wimpy, one motor driver will do). There are also male headers for RESET, RX, TX, 5V and GND.

On the other side of the MCU we have two female headers for digital pins 9-13 + AVCC and analog pins 0-5. I’m using analog pins 0-3 as digital pins 14-17 to drive the stepper motor that rotates the ultrasonic sensor. Analog 4 and 5 are I2C which I need for the compass module.

Digital pins 2-8 are used to drive the motor controller (3 and 6 are PWM pins so do the PWM bit, obviously).

That leaves digital pins 9-13 of which I need 9 and 10 for the stepper + 11 for an LED.

Two pins left. Fine. Better than 3 IO extenders really, isn’t it.

Will post more when I get the time. Have the stepper working already, waiting on more pins to assemble the ribbon cable for the rest of it and will also have to see what happens with the health of the furry one.

I really can’t believe what I tried to do before. “Keep It Simple Stupid”.

 

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