PIC’Spectrum—Robert Lacoste, Chaville, France
What is PIC’Spectrum? It’s an autonomous device able to display the frequency decomposition of an audio band signal.
Physically, PIC’Spectrum is a small box with a microphone or audio line input at one end and a standard VGA output connector on the other. It displays on the video monitor the spectrum of an incoming sound and updates it in real time (e.g., 10 refreshes per second).
Of course, PIC’Spectrum is a digital spectrum analyzer. The incoming signal is first digitized and its spectrum computed with a 256-point Fast Fourier Transform. The corresponding video image is software-generated on-the-fly.
This compact device has only three controls: a signal-level potentiometer, a run-hold switch, which freezes the display, and a log/lin switch, which switches the spectrum amplitude display between logarithmic and linear scales.
And, there’s no PC here. Apart from a voltage regulator and a quad-operational amplifier for signal amplification, the only other active component is the PIC17C756. Notably, the PIC has enough internal resources to do everything from signal acquisition to video generation through real-time FFT. The PIC therefore replaces the A/D converter, digital signal processor, and video generator, which make up the classic design of a digital spectrum analyzer.
You may notice that the PIC17C756 doesn’t have an integrated video controller. But, it does have enough horsepower and program memory to do software-generated video. All by itself, PIC’Spectrum directly drives the VGA CRT at a high level of quality.
So just where does the sky meet the ground?
With Sky Scanner, you can find out. Adam uses a miniature CCD camera and logic to capture a video image of the horizon. Based on the slope and offset of this line, the PIC17C44 determines the attitude of the sensor.
While conventional tilt sensors can do essentially the same thing, Sky Scanner has a distinct advantage. It’s immune to acceleration. It uses the horizon, not gravity, as a fixed reference. It measures 360° of roll, 70° of pitch, and processes about 25 updates per second.
Is it accurate? You betcha. It’s relative accuracy stands at ±1° and its absolute accuracy is limited only by the presence of obstructions.
Reid made this project not to win a contest, but in order to hear better. In 1989, he received a cochlear implant, which consists of a body-worn speech processor and a surgically implanted receiver/stimulator that includes an electrode array placed in the snail-shaped cochlea, deep in the skull. Essentially, a microphone in the earpiece picks up a sound, which the processor analyzes, digitizes, and encodes into an RF signal, which is then passed through the skin to the implanted receiver.
However, despite many adjustments, Reid’s speech recognition was sporadic and he could not use the phone. He came to realize that the EEPROM settings on his implant were wrong.
The solution: he uses a three processor system (PIC17C44, ‘17C42, and ‘16C74) which first intercepts, decodes, and modifies the RF datastream from his bodyworn implant speech processor before reconstructing a modified datastream that is applied to the implanted portion of the cochlear implant.
