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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

  • Having the IR receiver and Transmitter  on a daughter board and use a socket instead on the board allowing for the IR to be case mounted. After all this kind of board will end up in a case as  a final resting place for a home automation sensor etc

     

    Adding a small SOT temp sensor or something to complete the capability (Available in I2C as well)

     

    for the outputs, if you use an open collector drive arrangement then the user can choose whatever they want , maybe a solder pad bridge to connect a pull up if needed

     

    inputs could easily be protected by using a small val resistor and a protection diode 3v3 or 5v depending on the input, that way even exceeding the volts a bit would not break anything

     

    have a look at this for an idea of what i mean, I know it is for a TiviaC board but the integration techniques are the same

    http://www.ti.com/tool/boostxl-iobkout,there is a link to a schematic, look at the ESD protection in particular

     

    Oh and Very nice board btw,

Reply

  • Having the IR receiver and Transmitter  on a daughter board and use a socket instead on the board allowing for the IR to be case mounted. After all this kind of board will end up in a case as  a final resting place for a home automation sensor etc

     

    Adding a small SOT temp sensor or something to complete the capability (Available in I2C as well)

     

    for the outputs, if you use an open collector drive arrangement then the user can choose whatever they want , maybe a solder pad bridge to connect a pull up if needed

     

    inputs could easily be protected by using a small val resistor and a protection diode 3v3 or 5v depending on the input, that way even exceeding the volts a bit would not break anything

     

    have a look at this for an idea of what i mean, I know it is for a TiviaC board but the integration techniques are the same

    http://www.ti.com/tool/boostxl-iobkout,there is a link to a schematic, look at the ESD protection in particular

     

    Oh and Very nice board btw,

Children
  • in reply to Robert Peter Oakes

    Nice one about the IR  note that the Pi face has a 3 pin connector for the receiver , just do one each for rx & tx.

     

    The temp sensor is a good idea as well

     

    I'm assuming the extra Power connector is to drive the servo style outputs if so then great other wise you may need to get separate power to those!

     

    For the robot can we have some nice MEMS sensors on the I2c and maybe even an RTC ...(pushing the boat out !! image)