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Topic: PICqueño chipKIT/Arduino clone (Read 7091 times) previous topic - next topic

PICqueño chipKIT/Arduino clone

We're trying to get out the first home-brew chipKIT compatible board. It won't be as slick as the many Arduino clones because the chips are only in SMD, but we're making up a board with our own parts and ideas.

Here's the initial files. We'll make some swaps before routing:

*Replace passives (C, R, LED, button), FT232, USB jack, and transistors with our own parts
*Add a ferrite bead to the USB power supply pin (like we usually use)
*Swap in our SMD power jack, SMD button
*Add 10K/10K resistor voltage dividers to the analog pins. Just the pins that are normally on the Arduino (outer row?). This will let our design measure the full range of 5volt output from a shield, while the Digilent version is clamped at 3.3volts.

Also in SVN and a wiki page will be up shortly.

Name courtesy Sjaak. Original design by Digilent (CC BY-SA).
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Re: PICqueño chipKIT/Arduino clone

Reply #1
Silly question (really shows my ignorance wrt arduino).  I'm assuming the Arduino "analog" pins aren't meant to be general purpose I/O, meaning, bi-directional analog, bi-directional digital.

The reason I'm asking is that the divider would work well for sampling analog inputs, but not so well if you were trying to output a logic 0 and the other side had a pull-up (you'd wind up with 2.5V on the pin).

Again, hopefully a silly question, mainly rooted in my own unfamiliarity with the Arduino interface.

Re: PICqueño chipKIT/Arduino clone

Reply #2
I may have answered my own question:

http://http://www.arduino.cc/en/Tutorial/AnalogInputPins
Quote
Consequently, if a user needs more general purpose input output pins, and all the analog pins are not in use, the analog pins may be used for GPIO.

Is my concern with the divider well-founded?  It would probably work as a digital output with a high impedance digital input on the "shield", as long as it doesn't have a pull-up.

Re: PICqueño chipKIT/Arduino clone

Reply #3
You're totally right, I didn't think it all the way through.
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Re: PICqueño chipKIT/Arduino clone

Reply #4
[quote author="bearmos"]but not so well if you were trying to output a logic 0 and the other side had a pull-up (you'd wind up with 2.5V on the pin).[/quote]

This was assuming a 10k pull-up to 5V on the shield.

here's a quick sketch:
[attachment=0]

The concern is if pin on the PIC32 is to be used as a digital output and it tries to output a '0', the Arduino shield will see a 2.5V signal, due to the voltage divider made by R1 and R2.

Re: PICqueño chipKIT/Arduino clone

Reply #5
i like the idea of releasing our own version of the chipkit, adding an sdcard socket and other simple perferials could help attract more to use it

Re: PICqueño chipKIT/Arduino clone

Reply #6
[quote author="ian"]You're totally right, I didn't think it all the way through.[/quote]

that's the beauty of open-source and design reviews :)

i really like the idea of not clamping to 3.3V though.

i guess you could try and get fancy and maybe put some active circuitry in there, but i can't think of anything off the top of my head.  the other option might be to have a voltage divider that's jumper selectable?  not sure what kinds of cost/complexity this brings in though.

Re: PICqueño chipKIT/Arduino clone

Reply #7
[quote author="sqkybeaver"]adding an sdcard socket and other simple perferials could help attract more to use it[/quote]

The pic32 should have plenty of room for a nice FAT library too. This way, you could eliminate what would normally be another shield purpose.  I saw a nice library on HAD a while ago for FAT.

I guess the tricky part is coming up with the right mix of functionality/cost and getting it out the door in time.


Re: PICqueño chipKIT/Arduino clone

Reply #9
i was contemplating using the max32 as a base for a custom pcb for use in a cnc controller.

 

Re: PICqueño chipKIT/Arduino clone

Reply #10
[quote author="sqkybeaver"]i was contemplating using the max32 as a base for a custom pcb for use in a cnc controller.[/quote]

that's definitely deserving of it's own thread :)

Re: PICqueño chipKIT/Arduino clone

Reply #11
SD card is a good idea. Let's see how the positioning on the PCB goes, and then we can add in some extras - EEPROM, SD card, USB?
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Re: PICqueño chipKIT/Arduino clone

Reply #12
it would be a waste not to make use of the
• USB 2.0 On-The-Go Peripheral with integrated PHY
• 10/100 Ethernet MAC with MII/RMII Interfaces
that the pic32MX795F512 and most pic32 ofer.
best regards FIlip.

Re: PICqueño chipKIT/Arduino clone

Reply #13
Quote
was contemplating using the max32 as a base for a custom pcb for use in a cnc controller.

I am using pic32mx with sd card and some alegro drivers (6 stepper drivers, 5 fet's etc) for control of the reprap 3d printer for a while now (2+ years) and it works great. It's not my design (some uk company designed the board) but I'm designing a new board (modular design in contrary to this board that is single pcb solution) and working on new firmware (it will of course be open sourced when is done) ... I write this just to cinfirm that with 32mx you have more then enough cpu power to parse the g-code from the sd card and drive a fairly complex cnc (to drive a reprap you control temperature on 2 extruders, temperature of the bed, temperature of the envinronment, drive the heads in xyz + control plastic flow trough 2 extruders ... all that in sync :) )

As for the "let's make a 32mx dev board", one of the best I seen is this: http://www.mikroe.com/eng/products/view ... -pic32mx7/ is one of the nicest I seen so far and this one: http://www.mikroe.com/eng/products/view ... c32-board/ is the top selling one afaik.

So something like that is imho something that would be very interesting dev board if DP can make it cheaper (and I really believe this can be made for way below 100$)

Check out also
http://www.olimex.com/dev/stm32-103stk.html
http://www.olimex.com/dev/stm32-lcd.html

It would be cool to have something like this with pic32

I still believe it would be harder to solve the software side of things (to make all the needed libraries and examples for the board so it can be used with new "arduino for pic") then to design the board itself (I designed number of pic32 board, not a big deal.. especially if you have seeed backing you up to make pcb's and solder those nasty rasters :D

Re: PICqueño chipKIT/Arduino clone

Reply #14
i was thinking of a 2 board solution, one with the max32 core + lcd + sd card + rotatory encoder + buttons + isolated inputs, and another board with the stepper controller, relays, etc...

as i don't have any cnc equipment now something that could be ported from an avr based arduino would make it an easier project than starting from scratch.

or would just finding a board that has the connectors for the arduino mega work better.