is mated to the prototyping board via matching 0.1 inch
female header receptacles.
Dropping in the PIC
Okay. Now that we have a new radio for our ZeroG -
PIC24FJ128GA006 Trainer, the “ZeroG” original
development board name can now be considered “
XBee-PRO.” Our next modification will negate the development
board’s PIC moniker. Don’t be tempted to mount a ZeroG
module with the new 32-bit PIC installed, the SPI portal
used by the ZeroG module is replaced by USB mechanics on
the 32-bit PIC. Likewise, we should avoid utilizing the serial
port that we installed over in Nuts & Volts. The NV serial
port is tied to a dedicated ST3232 RS-232 voltage translator
IC. If we choose to, we can still use the ST3232-equipped
serial port to talk to other devices that need to see RS-232
voltage levels. However, the XBee-PRO will most likely
produce some magic smoke if we try to connect its TTL
serial interface to the ST3232’s bi-level RS-232 interface. As
you can see in Photo 5, the PIC32MX795F512H is laying
the PIC24FJ128GA006’s pad area like the egg of a brown-headed cowbird.
Doing the Paperwork
Schematics 1 and 2 document our engineering change
activity. If you grab your copy of this month’s Nuts & Volts,
you’ll notice that the PIC24FJ128GA006 in the Design Cycle
discussion has been replaced here by a PIC32MX795F512H.
Pretty much everything else remains the same with
absolutely no changes made in Schematic 2. However, if
you decide to use the ST3232-equipped serial port on the
PIC32MX795F512H’s RF4 and RF5, you’ll need to code for
UART3A instead of UART2. Note that the XBee-PRO module
is feeding from the PIC32MX795F512H’s UART2A tube.
As you can see in Photo 6, the hardware is assembled
and ready to test. The schematics have also been updated.
I’ve got my USB-XBEE-DONGLE CARRIER loaded with an
XBee-PRO module, and a Tera Term Pro emulator session is
running on my laptop. Let’s see if we can push some
characters out of the PIC32MX795F512H, through the
module, and into the terminal emulator window.
Microchip’s MPLAB C for PIC32 MCUs supports a
library of practical peripheral routines we can call upon for
our UART2A test code. To obtain access to the library, all
we need to do is include it in our source code:
MPLAB C for PIC32 MCUs
PHOTO 4. Here’s my caveman module adapter.
Note the point-to-point wiring for power, ground,
serial I/O, and the active-low RESET pins.
PHOTO 5. In addition to the PIC32MX795F512H, the
PIC24FJ128GA106 and PIC24FJ128GB106 can also
lie comfortably in this bed of pads.
SERVO 05.2010 57