Silicon Chip Online - DSP Musicolour Light Show; Pt.3

DSP MUSICOLOUR FEATURES

1. Selectable 8-band equaliser

2. Auto detection of mains frequency (50Hz or 60Hz)

3. Selectable phase-controlled or zero voltage-switched
output channels (8-bit resolution)

4. For each logical output channel:

(a) Selectable gain

(b) Selectable audio passband: arbitrary minimum
and maximum frequencies

(d) Selectable quiescent level (filament preheat)

(e) Selectable zero voltage mode, strobe mode,
direct mode or continuous mode

5. Selectable logical channel for each physical output channel

6. Chaser modes implemented as a virtual machine

7. Trigger channel with:

(a) Selectable audio passband

(b) Selectable trigger threshold

8. Firmware support for RC5 remote control (requires
additional PC board; to be described next month)

9. Firmware support for high speed UART (requires
additional PC board)

10. Selectable balance

11. Selectable display frequency, brightness and screen
saver time-out period

12. Selectable sampling frequency from 16kHz to 50kHz
simultaneous on all channels

13. Real time 7-bit FFT using double buffering

14. Persistent software settings and multiple non-volatile
user memories

15. Self calibration and Diagnostics

16. Automatic and manual tuning of the internal fast
RC oscillator for increased accuracy

17. Adaptive potentiometer controls

18. Silence detection and triggering

19. Input op amp stage clipping detection

While the circuit of the DSP Musicolour (published in June) may at first seem complicated, it is relatively simple when you consider all the features that we have been able to pack into this powerhouse. Check out the list opposite. We think you’ll agree!

We assume that you have read the first and second parts of the article in the previous two issues of SILICON CHIP. If you have followed the construction in last month’s issue, you should have a fully assembled DSP Musicolour in its case and you should have tested the supply rails at test points TP0 and TP1. These should have measured close to their correct values of +5V and +10V respectively.

If they do not measure close to these values, you should refer to the troubleshooting section below for further hints, although we mentioned some extra checks to perform in that case in last month’s issue, to which you should refer first.

Fig.1: block diagram of the DSP Musicolour. Use this in conjunction with the text to understand operation, programming and calibration.

In last month’s article, we mentioned that LK4 is optional and is normally omitted. When LK4 is omitted, the DSP Musicolour has three independent audio inputs which can be used to modulate the output channels. These are the Microphone input, the Left Audio channel and the Right Audio Channel.

The Left and Right Audio channels from the speaker terminals on the back panel are attenuated by the LEFT and RIGHT potentiometers on the front panel. The Microphone line input is a mix of the on-board electret microphone signal and any external microphone connected to the 6.5mm jack on the back panel.