Download Gergely Andor Maksay Wireless surface stimulator

for the extended Flash.
The MCU is available in a small, 28 pin Thin-Shrink Small Outline Package
(TSSOP), which could be soldered manually at the university.
Development tool
The MSP430F2122 was programmed and debugged with the MSPFET430UIF
Flash Emulation Tool (FET) via 2-wire JTAG (Spy-Bi-Wire) communication.
I built a programming interface board ( its schematic can be found in the Appendix ) which included a standard 14 pin JTAG connector and all external
components and signal connections which are only necessary for successful programming, but not for the correct operation of the device, after the programmer
was detached. The stimulator and the RS232/Wireless interfacing board can be
programmed after the MSPFET430UIF pod is connected to the JTAG connector andthe necessary connections are made with the programmed board. The
target board's power is supplied from the pod, therefore any on-board battery
must be deactivated.
Wireless communication
The CC1000 wireless transceiver chip has a 3-wire serial conguration interface
and a 2-wire serial data interface. Five GPIO pins of the microcontroller are
dedicated for handling communication with these interfaces using a technique
called 'bit banging'. At the data rate of 9.6 kbit/s the extra workload is negligible for a powerful microcontroller, like the MSP430[22].
A more detailed
discussion about the CC1000 chip can be found in Section 4.1.
Power supply
The MSP430F2122 MCU's supply voltage spans from 1.8V-3.6V, while that of
the CC1000 wireless transceiver ranges from 2.1-3.6V. With this in mind, a 3V
2032 Lithium Battery was chosen as power supply, which is situated on the back
side of the PCB. From such a battery the MCU can only run reliably with CPU
frequencies at 8 MHz. ( It must be mentioned, that there is no voltage regulator
on the design, which means that the supply voltage will decline with the aging
of the battery.
According to [17] both the MCU at 8 MHz and the CC1000
chip can work reliably with supply voltages over 2.2 V, which was considered
a fair safety margin. ) With the MSP430F2122's powerful RISC architecture I
found 8 MHz of master clock frequency acceptable for this application, and the
reduction of processing speed also reduced the current consumption of the IC.
5.1.2 Software description
One of the highlights of the MSP430 microcontroller is the ease, by which it can
switch between active mode and low power mode[19]. In order to utilise this
feature I assigned most of the tasks to peripherals, which trigger interrupts to
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