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

Nice board there Victor!

What are you using for the ADC and what does the PWM is that dedicated or an alternate use for the GPIO?

Have you considered some DAC channels as well?

If  you moved the NRF socket and the power decoupling a bit  you could offer the connector for the  extra I/O. i know it's not soldered but gives you an option.

Thanks for showing us you board

John

PCA9686 for the PWM.. I see it now ..Good one!

Very nice - recently, when I wanted a lot of PWMs (30) I used a Lattice ICE40 series ultra low power FPGA  - more work than 2 PCA9685s (not 9686 !) but similar price and much more flexible.

MK

I was wondering about the Chip ID but  Google found it as that so someone else must of made the same mistake

With the FPGA you could of got rid of the GPIO chip as well saving some real estate!

The only thing I could say is t hat you would obviously need experience of these chips then, I assume they are FLASH based to save chips etc???

Also were those the ones with the cool polar bear logo?

The ICE40's are one time prom programmable but any number of times RAM programmable so I keep the code in a serial flash and SPI it into the FPGA on boot up. The processor is a an STM32F100   - if anyone needs the FPGA boot code I'll share.

MK

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,

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 !! )

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!

@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 . 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

That's a real good effort there Victor I'm impressed at your work. You could bring out the I2C  to a connector and  you could have the MEMS sensors on  there as the EBAY ones are dirt cheap!!

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