📄 f06x_adc2_externalinput_mux.lst
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C51 COMPILER V8.08 F06X_ADC2_EXTERNALINPUT_MUX 02/14/2008 15:32:09 PAGE 1
C51 COMPILER V8.08, COMPILATION OF MODULE F06X_ADC2_EXTERNALINPUT_MUX
OBJECT MODULE PLACED IN F06x_ADC2_ExternalInput_Mux.OBJ
COMPILER INVOKED BY: C:\SiLabs\MCU\IDEfiles\C51\BIN\C51.exe F06x_ADC2_ExternalInput_Mux.c DB OE
line level source
1 //-----------------------------------------------------------------------------
2 // F06x_ADC2_ExternalInput_Mux.c
3 //-----------------------------------------------------------------------------
4 // Copyright 2005 Silicon Laboratories, Inc.
5 // http://www.silabs.com
6 //
7 // This code example illustrates using the internal analog multiplexer to
8 // measure analog voltages on up to 8 different analog inputs. Results are
9 // printed to a PC terminal program via the UART.
10 //
11 // The inputs are sequentially scanned, beginning with input 0 (AIN2.0), up
12 // to input number <ANALOG_INPUTS>-1 (maximum ANALOG_INPUTS = 8, which will
13 // scan all analog inputs AIN2.0 - AIN2.7).
14 //
15 //
16 // ADC Settling Time Requirements, Sampling Rate:
17 // ----------------------------------------------
18 //
19 // The total sample time per intput is comprised of an input setting time
20 // (Tsettle), followed by a conversion time (Tconvert):
21 //
22 // Tsample = Tsettle + Tconvert
23 //
24 // Settling and conversion times may overlap, as the ADC holds the value once
25 // conversion begins. This code example takes advantage of this to increase
26 // the settling time above the minimum required. In other words, when
27 // converting the value from analog input Ain(n), the input mux is switched
28 // over to the next input Ain(n+1) to begin settling.
29 //
30 // |--------Settling Ain(n)--------|=Conversion Ain(n)=|
31 // |--------Settling Ain(n+1)--------|=Conversion Ain(n+1)=|
32 // |--------Settling Ain(n+2)--------|
33 // ISR: Timer 2 ^ ^ ^
34 // ISR: ADC2 ^ ^
35 //
36 // The ADC input voltage must be allowed adequate time to settle before the
37 // conversion is made. This settling depends on the external source
38 // impedance, internal mux impedance, and internal capacitance.
39 // Settling time is given by:
40 //
41 // | 2^n |
42 // Tsettle = ln | --- | * Rtotal * Csample
43 // | SA |
44 //
45 // In this application, assume a 100kohm potentiometer as the voltage divider.
46 // The expression evaluates to:
47 //
48 // | 2^12 |
49 // Tsettle = ln | ---- | * 105e3 * 10e-12 = 10.2uS
50 // | 0.25 |
51 //
52 // In addition, one must allow at least 1.5uS after changing analog mux
53 // inputs or PGA settings. The settling time in this example, then, is
54 // dictated by the large external source resistance.
55 //
C51 COMPILER V8.08 F06X_ADC2_EXTERNALINPUT_MUX 02/14/2008 15:32:09 PAGE 2
56 // The conversion is 16 periods of the SAR clock <SAR_CLK>. At 2.5 MHz,
57 // this time is 16 * 400nS = 6.4 uS.
58 //
59 //
60 // Tsample, minimum = Tsettle + Tconvert
61 // = 10.2uS + 6.4uS
62 // = 16.6 uS
63 //
64 // Timer 2 is set to change the mux input and start a conversion every 20uS.
65 //
66 // General:
67 // --------
68 //
69 // The system is clocked using the internal 24.5MHz oscillator. Results are
70 // printed to the UART from a loop with the rate set by a delay based on Timer 2.
71 // This loop periodically reads the ADC value from a global array, Result.
72 //
73 // The ADC makes repeated measurements at 20uS intervals based on Timer 2.
74 // The end of each ADC conversion initiates an interrupt which calls an
75 // averaging function. <INT_DEC> samples are averaged then the Result
76 // values updated.
77 //
78 // For each power of 4 of <INT_DEC>, you gain 1 bit of effective resolution.
79 // For example, <INT_DEC> = 256 gain you 4 bits of resolution: 4^4 = 256.
80 //
81 // The ADC input multiplexer is set for a single-ended input. The example
82 // sequentially scans through the inputs, starting at AIN0.0. <ANALOG_INPUTS>
83 // inputs are read. The amplifier is set for unity gain so a voltage range of
84 // 0 to Vref (2.43V) may be measured. Although voltages up to Vdd may be
85 // applied without damaging the device, only the range 0 to Vref may be
86 // measured by the ADC. The input is available at the 8-position board-edge
87 // connector, J20, on the C8051FX20-TB.
88 //
89 // A 100kohm potentiometer may be connected as a voltage divider between
90 // VREF and AGND as shown below:
91 //
92 // ---------
93 // |
94 // 8 o| AGND ----|
95 // o| VREF ----|<-|
96 // o| AIN2.0 | |
97 // o| | |
98 // o| --------
99 // o|
100 // o|
101 // 1 o|
102 // |
103 // ---------
104 //
105 // How To Test:
106 //
107 // 1) Download code to a 'F06x device that is connected to a UART transceiver
108 // 2) Connect serial cable from the transceiver to a PC
109 // 3) On the PC, open HyperTerminal (or any other terminal program) and connect
110 // to the COM port at <BAUDRATE> and 8-N-1
111 // 4) Connect a variable voltage source (between 0 and Vref)
112 // to AIN2.0 - AIN2.7, or a potentiometer voltage divider as shown above.
113 /// AIN2.0 - AIN2.7 are shared with the Port1 pins available on J12
114 // 5) HyperTerminal will print the voltages measured by the device if
115 // everything is working properly. Note that some of the analog inputs are
116 // floating and will return nonzero values.
117 //
C51 COMPILER V8.08 F06X_ADC2_EXTERNALINPUT_MUX 02/14/2008 15:32:09 PAGE 3
118 // Target: C8051F06x
119 // Tool chain: Keil C51 7.50 / Keil EVAL C51
120 // Command Line: None
121 //
122 //
123 // Release 1.0
124 // -Initial Revision SM
125 // -21-July-06
126 //
127
128
129 //-----------------------------------------------------------------------------
130 // Includes
131 //-----------------------------------------------------------------------------
132
133 #include <c8051f060.h> // SFR declarations
134 #include <stdio.h>
135
136 //-----------------------------------------------------------------------------
137 // 16-bit SFR Definitions for 'F06x
138 //-----------------------------------------------------------------------------
139
140 sfr16 DP = 0x82; // data pointer
141 sfr16 RCAP2 = 0xCA; // Timer2 reload/capture value
142 sfr16 RCAP3 = 0xCA; // Timer3 reload/capture value
143 sfr16 RCAP4 = 0xCA; // Timer4 reload/capture value
144 sfr16 TMR2 = 0xCC; // Timer2 counter/timer
145 sfr16 TMR3 = 0xCC; // Timer3 counter/timer
146 sfr16 TMR4 = 0xCC; // Timer4 counter/timer
147 sfr16 ADC2 = 0xBE; // ADC2 data
148 sfr16 ADC0GT = 0xC4; // ADC0 greater than window
149 sfr16 ADC0LT = 0xC6; // ADC0 less than window
150 sfr16 DAC0 = 0xD2; // DAC0 data
151 sfr16 DAC1 = 0xD2; // DAC1 data
152 sfr16 CAN0DAT = 0xD8; // CAN data window
153
154 //-----------------------------------------------------------------------------
155 // Global Constants
156 //-----------------------------------------------------------------------------
157
158 #define BAUDRATE 115200 // Baud rate of UART in bps
159 #define SYSCLK 24500000 // Output of PLL derived from (INTCLK*2)
160 #define INT_DEC 256 // Integrate and decimate ratio
161 #define SAR_CLK 2500000 // Desired SAR clock speed
162
163 #define SAMPLE_DELAY 250 // Delay in ms before displaying sample
164
165 #define ANALOG_INPUTS 8 // Number of AIN pins to measure
166 // (min=1, max=8)
167
168 sbit LED = P1^6; // LED: '1' = ON; '0' = OFF
169
170
171 //-----------------------------------------------------------------------------
172 // Function Prototypes
173 //-----------------------------------------------------------------------------
174
175 void OSCILLATOR_Init (void);
176 void PORT_Init (void);
177 void UART1_Init (void);
178 void ADC2_Init (void);
179 void TIMER2_Init (void);
C51 COMPILER V8.08 F06X_ADC2_EXTERNALINPUT_MUX 02/14/2008 15:32:09 PAGE 4
180 void ADC2_ISR (void);
181 void TIMER2_ISR (void);
182 void Wait_MS (unsigned int ms);
183
184 //-----------------------------------------------------------------------------
185 // Global Variables
186 //-----------------------------------------------------------------------------
187
188 long Result[ANALOG_INPUTS]; // ADC2 decimated value, one for each
189 // analog input
190 unsigned char amux_input=0; // index of analog MUX inputs
191 unsigned char amux_convert=0;
192
193
194 //-----------------------------------------------------------------------------
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