WM8750-EV1M
SOFTWARE INTERFACE
When using the WM8750-EV1B evaluation board with a DSP platform, the registers may be
set using the supplied software with a PC and parallel port cable as shown in Figure 29.
If the DSP is used to write to the WM8750 registers as well as supplying/receiving the audio
interface timing and data signals, it is recommended that twisted pair or shielded wires are
used to connect the DSP platform to the WM8750-EV1B. If the DSP supplies are set to the
same voltage as the DBVDD supplies of the WM8750, a direct connection can be made to
pin 6 (CSB), pin 7 (SDIN) and pin 8 (SCLK) of header strip J13 for 3-wire software mode as
shown in Figure 30. If the DSP is running at a higher voltage (e.g. +5V) than the WM8750,
the signals from the DSP platform should be connected to test points TP2 (CSB), TP4
(SDIN) and TP3 (SCLK). Connecting the higher voltage signals from the DSP to the test
points will level shift through the transistors down to the same level as the DBVDD supply as
shown in Figure 31. This will ensure that the WM8750 input CMOS thresholds (i.e. Logic
High (min) = DBVDDx0.7; Logic Low (max) = DBVDDx0.3) are met and the device will not be
damaged.
The same connections apply for controlling the WM8750 via 2-wire software mode (i.e. only
pin 7 (SDIN) and pin 8 (SCLK) of header strip J13 are used). Pin 6 (CSB) can be pulled low
on the board if device address 0011010 [0x34h] is required or pulled high address 0011011
[0x36h] is required.
CONNECTION DIAGRAMS
m
Software
Control
WM8750-EV1B
J13
Audio
Interface
DSP
H1
Platform
J15
J17
J21
Figure 29 DSP Connection with PC Control using Wolfson Software
Rev 2.0, February 2005
40
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
