Hardware Reference
In-Depth Information
Photo 2.17
Measurement Computing Corporation's PMD-1208LS Personal
Measurement Device
The PMD-1208LS USB device
The PMD-1208LS is an example of a modern and highly versatile USB
device suitable for a wide variety of data acquisition and control applications.
Whilst it was designed for slower USB 1.1 ports, the device is compatible
with USB 2.0 ports and is supported under Microsoft Windows 98SE/ME/
2000 and XP.
The PMD-1208LS features eight analogue inputs, two 10-bit analogue out-
puts, 16 digital I/O connections and one 32-bit event counter. The device is
powered by the
+
5 V USB supply and does not require any external power
source. The PMD-1208LS's analogue inputs are software configurable for either
eight 11-bit single-ended inputs, or four 12-bit differential inputs. An on-board
industry standard 82C55 programmable peripheral interface (see page 29) pro-
vides the 16 discrete digital I/O lines. Each digital channel can be configured
for either input or output.
The block schematic diagram of the PMD-1208LS is shown in Figure 2.31.
All I/O connections are made to the screw terminals located along each side of
the device.
The PMD-1208LS is supplied with configuration software as well as Univer-
sal and OEM Software Libraries. Using these libraries it is a relatively simple
matter to program applications using 32-bit Windows development software
such as Microsoft Visual C
++
and Microsoft Visual Basic. As an example, the
following Visual basic code is all that is required to produce a simple digital
frequency meter (see Figure 2.32).
