PHOTO 2. This is an overhead view of the
Cerebot 32MX7's JPA Pmod portal which is
configured to power a 3. 3 volt Pmod or
user-designed device. Note the POWER
SELECT header (J16) is jumpered to power
the Cerebot 32MX7 using external power.
The external power supply can be
connected at J17 or J18.
the PIC32MX795F512L’s silicon is
exposed in the Cerebot 32MX7 design.
The 32MX7’s silicon “blades” are made
up of Pmod I/O portals, a USB
host/device/OTG subsystem, a 10
Mbps/100 Mbps Ethernet subsystem,
two independent CAN networks, and a
pair of I2C interfaces.
Cerebot 32MX7
Pmod Portals
The Cerebot I/O complex includes six powered I/O
portals designed to accommodate the growing family of
Digilent Pmod (Peripheral Module) accessory modules. Each
Pmod portal consists of eight lines of PIC32MX795F512L
I/O and jumper selectable voltages of + 5.0 VDC and + 3. 3
VDC with accompanying electrical ground connections. In
addition, each of the eight I/O lines is protected from ESD
and short circuits. The 12-pin JPA Pmod portal captured in
Photo 2 is configured to power a 3. 3 volt Pmod device
using external power.
Although Digilent Pmods are design marvels in
themselves, there’s no reason why your version of a Pmod
can’t take advantage of the 32MX7’s Pmod portals. For
instance, Schematic 1 tells us that Pmod portal JPA
exposes a subset of the PIC32’s port B I/O pins. Pmod
portal JPA also supplies access to the majority of the
PIC32’s comparator resources and some of the analog-to-digital inputs. If your personal Pmod needs eight logically
consecutive I/O pins, JPB provides access to port E I/O pins
RE0 through RE7. As you’ve already ascertained, each Pmod
portal has a differing mix of PIC32MX795F512L I/O. This
Pmod portal I/O mix allows you to choose a particular
Pmod portal and design your personal Pmod device around
the selected Pmod’s I/O configuration.
Cerebot 32MX7 USB
The 32MX7’s USB circuitry supports USB 2.0 Host, USB
2.0 Device and, OTG (On-The-Go). The Cerebot’s USB
subsystem can be configured as a USB full speed device or
a USB low speed device. USB connectivity is achieved via
the PIC32MX795F512L’s built-in USB 2.0 engine, a Type A
USB connector, and a Mini-AB interface. The 32MX7 can
operate as a self-powered USB device or a bus-powered
USB device. USB host operation is also possible as the
SCHEMATIC 1. The schematic
representation of JPA is typical of all
of the Pmod portals. Since the
Pmod portals are standard 0.1 inch
pitch female headers, you can easily
adapt your own garage-engineered
modules to the Cerebot 32MX7's
Pmod portals.
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