An Audio Interface Using the
TMS320F243 DSK and the TMS320LF2407 DSK
Description of Circuit
Note that this schematic on the following page is not of audio quality. However, it is
good enough to demonstrate at low cost how digital filtering can be achieved using the
TMS320F243 DSK and the TMS320LF2407 DSK.
Example code is provided in C for the TMS320LF2407 DSK.
Equipment Required
Signal generator or audio source
Oscilloscope or audio amplifier
Application for TMS320LF2407 DSK: FIR
Provides a low-pass filter and a comb filter. Other filters included are a high-pass filter
and an assembly language version of the low-pass filter.
If a signal generator is not available, then the filter can be tested by supplying a DC
voltage using a potentiometer to ADCIN0. If the program is compiled then run using
the animate option, then it can be seen how the output changes.
The TMS320LF2407 C code is provided in the directory FIR.
Application for the TMS320LF2407DSK: IIR
Infinite Impulse Response filters (IIR) can be used to implement filters using less terms
than does the equivalent Finite Impulse Response Filter (FIR). On the negative side, they
have the disadvantage of being potentially unstable.
The code for this application is in the directory IIR.
Application for the TMS320LF2407 DSK: FFT
Performs an 8-point Fast Fourier Transform (FFT). The FFT is performed 500 times per
second and can be used to detect frequencies of 62.5 Hz, 125 Hz and 250 Hz. In order to
detect more frequencies, then the number of points can be increased to 16, 32 etc.
The software uses a timed interrupt to control the FFT.
The code for this application is in the directory FFT.
References:
Assembly language tutorials included as part the CD
Rulph Chassaing. Digital Signal Processing with C and the TMS320C30
Data sheet for Burr-Brown OPA2337 rail-to-rail operational amplifier. sbo077.pdf
Click To View
Template…… A basic project for the TMS320LF2407 DSK. Configures an analog-to-digital converter
and generates a pulse width modulation (PWM) output.
To View Applications Please Click
Signal Generation………... TMS320LF2407 DSK: Sine
Audio Interface……...……TMS320LF2407 DSK: FIR
TMS320LF2407DSK: IIR
TMS320LF2407 DSK: FFT
Motor Control……………...TMS320LF2407 DSK: Stepper Motor
TMS320LF2407 DSK: DC Motor
Click here to view...........
Schematic 2 Below ↓
Route Map
1
2
4
3
AUDIO INTERFACE FOR TMS320F243 DSK / TMS320LF2407 DSK
D
3.3V
C1
10 uF
U1
VOLTAGE REG 3.3V
3
Vout
Vin
D
5V
5V
1
C3
10 uF
2
C2
100 nF
GND
3.3V
0V
1 kHz LOWPASS FILTER
SIGNAL OUT 1
R1
R2
160 k
1k6
C4
1 nF
T1PWM
C5
100 nF
0V
0V
1 kHz LOWPASS FILTER
C
SIGNAL OUT 2
R3
R4
160 k
1k6
C6
1 nF
T2PWM
C7
100 nF
0V
3.3V
P2
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
C
3.3V
40PIN
R6
220 k
AUDIO INPUT
P3
C8
220 nF
VR1
10 k LINEAR
R5
100 k
TEST INPUT
B
U2
OPA2337
PHONEJACK
R7
1k0
3.3V
REFERENCE
AUDIO IN
R8
1k0
R9
1k0
P1
ADC0
ADC1
ADC2
R10
10 k
1.65V
R11
10 k
C9
22 uF
0V
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0V
20PIN
3.3V ANALOG REFERENCE
3.3V
L1
100 uH
TMS320F243 DSK ONLY
A
A
C10
10 uF
C11
100 nF
Title
0V
AUDIO INTERFACE FOR TMS320F243 DSK / TMS320LF2407 DSK
Size
Number
A4
Date:
File:
1
2
1-Jul-2001
C:\CLIENT\SCH3\AUDIO.SCH
3
Revision
1
Sheet of
Drawn By: RICHARD SIKORA
4