USB PIC24 and PIC32 SPDIP Arduino

PIC24FJ64GB002 shown

Microchip has just released a SPDIP-28 PIC32.  This chip is pin compatible with the PIC24 which I have been developing for, and my latest toying has been with Arduino style boards, so I was determined to combine the two.

In the last week I have developed a prototype USB Arduino format board using a PIC24 or PIC32 as its CPU.  The Arduino format consists of the standardized 8 and 6 pin headers for I/O and power.  This was accomplished starting with an empty Arduino shield prototype board and building up as a PIC single board computer instead of a shield.  Now standard shields can be attached to this board.

The two CPUs I am targeting to support with this board are PIC24FJ64GB002 and the recently released PIC32MX220F032B.

The power circuit, ICSP (on left), and USB have been tested.  The PIC24 running a CDC (Serial over USB) project is recognized by the host PC.  Next step is to test the FTDI serial connector (on right), and all the analog/digital pins.  Following that is to add a crystal and capacitors to get USB support for the PIC32 (I wonder if I can do that on a shield?). All pins are exposed via the Arduino shield interface, so it is super expandable.  The red LED is for 5V power, and the green LED is for 3V3 power.  The button is the reset switch.  No user I/O are provided, must be accomplished by add ons.

The missing piece is the Arduino development environment support for PIC24 and this low end PIC32 chip.  That's a pretty big missing piece.  For now I can develop using Microchip's MPLAB 8 and MPLAB X.  I am hoping to use the chipKIT Arduino Development Environment for this board soon as it would be nice to program with Arduino sketches and C++. 

PIC32MX220F032B shown

Underbelly

PIC24 USB + Serial Development Board

Two main emphasis of this board are USB and Serial as well as using socketed components.  The 28-pin PIC24FJ64GB002 can perform as either a USB host or USB device, using jumpers to select between the connected USB socket.  The USB jumpers are also configured so when the PIC is USB host using the USB-A connector to attach a thumb drive, the USB-B connector may be configured to attach to an FTDI FT232RL chip to act as USB serial.  Using a USB-A to USB-B adapter, both the PIC and the FTDI chips could be active as USB devices. 

Two serial channels are jumpered for either RS-485 or RS-232 (DB-9 connectors not shown), or the second serial channel can be jumpered to the FTDI USB serial connection.  As configured here, RS-485 uses RX/TX with RTS to select whether reading or writing.  RS-232 can use RX/TX with CTS/RTS.  The ICSP (in circuit serial programming) connection in the lower left works with ICD or PICKit programmers, and shares the lines that provide CTS/RTS, so jumpers are provided to choose between those functions.  The PIC24 has quite a few 5V tolerant inputs, but I ran out of enough of them, so a 5V/3V3 logic level conversion board is socketed to read the CTS lines at 3.3V from the 5V MAX232 and MAX233. 

Voltage regulators are included to power 3.3V and 5V buses, accepting power from USB or 7V-12V external power.  Each module has a power jumper to effectively disable them.  The USB sockets have jumpers to selectively attach power to the 5V bus.

One SPI channel is also configured, allowing connection of features such as a micro SD card and/or SPI Ethernet.  This board specifically supports connection of a Microchip's PICtail Ethernet (ENC28J60) board.