Biomedical Engineering Reference
In-Depth Information
external. Coupled with the desire to be portable we need connecters that have many pins and yet
small enough to not enlarge the system. In addition, we need to be able to provide support function-
ality such as debugging and test beds.
The first connection type must be able to mate with the analog modules and provide a suitable
amount of connections, and yet be strong and compact enough to support another attached printed
circuit board. For the NSP, we use two connectors that allow for 80 different connections between the
boards. With this amount of connections, we can not only support current needs from an analog module
[duke], we can also support other daughter boards that may be designed for testing or future boards.
The second connection type is more inline with debugging and programming the DSP, CPLD,
and MSP. In addition, to retain the ability to communicate to systems that may be at great distances
we chose to design a flex connecter interface. On these connectors we provide access to the CPLD
jtag, MSP serial ports, wireless serial port, and other general CPLD IO for multiplexing communica-
tion between the components of the NSP. Finally, the connector layout is such that it allows for stack-
able modules, providing flexibility for all the three modes of operations described above.
3) Power Subsystem. The two different voltage requirements for the NSP are 1.8 and 3.3 V.
These voltages are not only used by the DSP, they are also used for the other hardware modules in
the system. In trying to supply the NSP components, the voltages can be supplied from multiple
pathways to the NSP. This includes an on-board option and off-board. The main option for power
supplying is from on-board. This includes a Texas Instruments TPS70351 Dual-Output LDO
Voltage Regulator that provides both 1.8 and 3.3 V voltages on a single chip and only requires 5 V
to operate. This chip also provides the power-up sequence required by the DSP once it is initialized.
In addition, requiring a single supply is very desirable for a portable system because only one 5-V
battery supply is necessary. With the off-board option, we can power the regulator through the flex
connectors, interconnect connector or a simple header; this way, a battery or external supply can
power the regulator. In addition, we can have the analog module or debugging system provide the
individual power requirements. This allows for the isolation of certain components for being pow-
ered. With such variability, future hardware can take advantage of the different powering options.
System Software.
There are six layers of software in the NSP system environment: 1) PC soft-
ware, 2) DSP operating system (OS), 3) DSP algorithms, 4)VHDL code 5) MSP430 code, and
6) client/server code. We wrote a PC console program to interface the DSP through the USB. The
console program calls functions within the DSP OS to initiate and control the USB communication
functions. The DSP OS is also responsible for reading/writing memory locations and various pro-
gram control functions. This is the main pathway for debugging the system. In tandem with the OS
layer of the DSP, there is low-level MSP code for initializing and controlling the wireless controller.
This code must interact with the DSP OS and any client code or algorithms that are running simul-
