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My rPI Shield: 16 PWM + 16 GPIO + 4 16 bit ADC + Extras!

vitormhenrique

Hello everyone,

 

So, recently I started working on a robot project, I own one of those rover 5 robot platform, and wanted to control it with my rPI. The problem is that the controller board utilizes +5V PWM signals, I would need ADC inputs to read the current drawn from the motors, and some +5V enable GPIO for other stuff.

 

I could use one level shifter to do the job, and many other IC chips for each other feature, but I ended up creating one shield for my rPI that had it all, I named it the "tauShield".

 

All the features are:

  • 16 PWM, 12-bit PWM (frequency from 40 Hz to 1000 Hz)
  • 4 16-Bit Analog-to-Digital IO's
  • 16 GPIO'S through an expander IC
  • 8 native rPI GPIO with +5V logic input / output
  • IR emitter / receiver
  • nRF24L01 adaptor (ultra low power 2Mbps RF transceiver for the 2.4GHz , excellent to talk to Arduinos, remote control the robot, etc...)

 

Ordered the PCB from oshpark:

image

 

After 1 hour of hand soldering, the result:

 

image

The shield also has a power jack that power the Raspberry PI with a overcurrent protection. The IC's share a I2C bus, the address of each IC can be changed soldering the jumper pads.

 

This is my first real "board" and I already noticed some stuff that can be improved, but it is working like a charm.

 

I still have extra 2 boards of this revision, and 2 from the first revision (does not have the GPIO expander and utilizes sparkfun's nRF24L01 adaptor), if anybody is interested let me know, I would need to hand solder it and ship to you.

 

So what do you guys think of my shield? suggestions? improvements? what is missing?

 

Couple more pictures:

 

image

image

 

Best regards,

 

Vitor Henrique

Parents

  • Thanks everyone for the feedback!

     

    I'm a Chemical Engineer, never studied electronic on school and I'm learning everything reading datasheets and books. I'm the worst on routing vias and placing the components on the PCB, routing this board was a nightmare, even with so much space! image

     

    @John Alexander I did not include a DAC because I could not find a use case yet on my robot, and left the extra IO's of the rPI (v2) out because I felt that I had enough IO's, but I'll add it on revision 3! The power connector it is intent to drive some (micro) servos, but it also can power the rPI. The big CAP there is to avoid power fluctuations shutting down the rPI, I tested with 5 micro servos, with no load, and it was ok. There is one PTC under the shield that I can desolder and completely separate the power supply, but i'll add a switch next revision as well.

     

    @Michael Kellett Cool!  I did not thought about FPGA because I never used it before (it is on my to do list to learn), the I2C IC's it is not the fastest / flexible way, but it works fine to accomplish a lot of stuff , and there is plenty documentation on line, example python codes, etc.

     

    @Peter Oakes initially this board was thought to be on my robot, not inside any case, that is why the IR is soldered on the "main board". I was thinking on adding gyroscope + accelerometer compass + barometric/temperature sensors, but that would make the board to expensive image. The 8 rPI IO's that i broke down leveled shifted to +5V are actually using use an open collector arrangement with a pull up resistor.

     

    One thing that i completely forgot is to give the user access to the level shifted I2C.

     

    Thank you guys,

     

    Vitor Henrique

  • in reply to vitormhenrique

    If the board is designed for the extras like gyro, temp etc, you can always leave then unpopulated for cost saving and only add if requested or the end user could do that if desired and having the skills of course

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