?? f31x_adc0_externalinput_mux.lst
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C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT_MUX 07/28/2008 14:50:43 PAGE 1
C51 COMPILER V8.08, COMPILATION OF MODULE F31X_ADC0_EXTERNALINPUT_MUX
OBJECT MODULE PLACED IN F31x_ADC0_ExternalInput_Mux.OBJ
COMPILER INVOKED BY: E:\Apps\Keil\C51\BIN\c51.exe F31x_ADC0_ExternalInput_Mux.c DB OE
line level source
1 //-----------------------------------------------------------------------------
2 // F31x_ADC0_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 (P1.0), up
12 // to input number <ANALOG_INPUTS>-1 based on the values in <PIN_TABLE>.
13 //
14 //
15 // ADC Settling Time Requirements, Sampling Rate:
16 // ----------------------------------------------
17 //
18 // The total sample time per input is comprised of an input setting time
19 // (Tsettle), followed by a conversion time (Tconvert):
20 //
21 // Tsample = Tsettle + Tconvert
22 //
23 // Settling and conversion times may overlap, as the ADC holds the value once
24 // conversion begins. This program takes advantage of this to increase the
25 // settling time above the minimum required. In other words, when
26 // converting the value from analog input Ain(n), the input mux is switched
27 // over to the next input Ain(n+1) to begin settling.
28 //
29 // |---Settling Ain(n)---|=Conversion Ain(n)=|
30 // |---Settling Ain(n+1)---|=Conversion Ain(n+1)=|
31 // |---Settling Ain(n+2)---|
32 // ISR: Timer 2 ^ ^ ^
33 // ISR: ADC0 ^ ^
34 //
35 // The ADC input voltage must be allowed adequate time to settle before the
36 // conversion is made. This settling depends on the external source
37 // impedance, internal mux impedance, and internal capacitance.
38 // Settling time is given by:
39 //
40 // | 2^n |
41 // Tsettle = ln | --- | * Rtotal * Csample
42 // | SA |
43 //
44 // In this application, assume a 100kohm potentiometer as the voltage divider.
45 // The expression evaluates to:
46 //
47 // | 2^12 |
48 // Tsettle = ln | ---- | * 105e3 * 10e-12 = 10.2uS
49 // | 0.25 |
50 //
51 // In addition, one must allow at least 1.5 us after changing analog MUX
52 // inputs or PGA settings. The settling time in this example, then, is
53 // dictated by the large external source resistance.
54 //
55 // The conversion is 16 periods of the SAR clock. At 2.5 MHz,
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT_MUX 07/28/2008 14:50:43 PAGE 2
56 // this time is 16 * 400nS = 6.4 uS.
57 //
58 //
59 // Tsample, minimum = Tsettle + Tconvert
60 // = 10.2uS + 6.4uS
61 // = 16.6 uS
62 //
63 // Timer2 is set to change the MUX input and start a conversion every 20 us.
64 //
65 // General:
66 // --------
67 //
68 // The system is clocked using the internal 24.5MHz oscillator. Results are
69 // printed to the UART from a loop with the rate set by a delay based on
70 // Timer0. This loop periodically reads the ADC value from a global array,
71 // <RESULT>.
72 //
73 // The ADC makes repeated measurements at 20 us intervals based on Timer2.
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 P1.0. <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.
87 //
88 // A 100 kohm potentiometer may be connected as a voltage divider between
89 // VREF and AGND as shown below:
91 // ---------
92 // |
93 // o| AGND ----|
94 // o| VREF ----|<-|
95 // o| P1.x | |
96 // o| | |
97 // o| --------
98 // o|
99 // o|
100 // o|
101 // |
102 // ---------
103 //
104 // How To Test:
105 //
106 // 1) Download code to a 'F31x device that is connected to a UART transceiver
107 // 2) Verify the TX and RX jumpers are populated on J3.
108 // 3) Connect a serial cable from the DB9 connector to a PC
109 // 4) On the PC, open HyperTerminal (or any other terminal program) and connect
110 // to the COM port at <BAUDRATE> and 8-N-1
111 // 5) Connect a variable voltage source (between 0 and Vref) to the Port1 pins,
112 // or a potentiometer voltage divider as shown above.
113 // 6) HyperTerminal will print the voltages measured by the device if
114 // everything is working properly. Note that some of the analog inputs are
115 // floating and will return nonzero values.
116 //
117 // Target: C8051F31x
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT_MUX 07/28/2008 14:50:43 PAGE 3
118 // Tool chain: Keil C51 7.50 / Keil EVAL C51
119 // Command Line: None
120 //
121 // Release 1.0
122 // -Initial Revision (SM / TP)
123 // -19 OCT 2006
124 //
125
126
127 //-----------------------------------------------------------------------------
128 // Includes
129 //-----------------------------------------------------------------------------
130
131 #include "c8051F310.h" // SFR declarations
132 #include <stdio.h>
133
134 //-----------------------------------------------------------------------------
135 // 16-bit SFR Definitions for 'F31x
136 //-----------------------------------------------------------------------------
137
138 sfr16 TMR2RL = 0xCA; // Timer2 reload value
139 sfr16 TMR2 = 0xCC; // Timer2 counter
140 sfr16 ADC0 = 0xBD; // 10-bit ADC0 result
141
142 //-----------------------------------------------------------------------------
143 // Global CONSTANTS
144 //-----------------------------------------------------------------------------
145
146 #define SYSCLK 24500000 // SYSCLK frequency in Hz
147 #define BAUDRATE 115200 // Baud rate of UART in bps
148 #define ANALOG_INPUTS 6 // Number of AIN pins to measure,
149 // skipping the UART0 pins
150 #define INT_DEC 256 // Integrate and decimate ratio
151
152 #define TIMER0_RELOAD_HIGH 0 // Timer0 High register
153 #define TIMER0_RELOAD_LOW 255 // Timer0 Low register
154
155 //-----------------------------------------------------------------------------
156 // Function PROTOTYPES
157 //-----------------------------------------------------------------------------
158
159 void Oscillator_Init (void);
160 void Port_Init (void);
161 void Timer2_Init(void);
162 void ADC0_Init(void);
163 void UART0_Init (void);
164
165 void Timer0_wait(int ms);
166
167 //-----------------------------------------------------------------------------
168 // Global Variables
169 //-----------------------------------------------------------------------------
170
171 long RESULT[ANALOG_INPUTS]; // ADC0 decimated value, one for each
172 // analog input
173
174 // Port1 ADC Inputs
175 unsigned char idata PIN_TABLE[ANALOG_INPUTS] = {0,1,2,3,4,5};
176
177 unsigned char AMUX_INPUT = 0; // Index of analog MUX inputs
178
179 //-----------------------------------------------------------------------------
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT_MUX 07/28/2008 14:50:43 PAGE 4
180 // MAIN Routine
181 //-----------------------------------------------------------------------------
182 void main (void)
183 {
184 1 unsigned char i;
185 1 unsigned long measurement;
186 1
187 1 PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer
188 1 // enable)
189 1
190 1 Oscillator_Init (); // Initialize system clock to
191 1 // 24.5MHz
192 1 Port_Init (); // Initialize crossbar and GPIO
193 1 Timer2_Init(); // Init Timer2 to generate
194 1 // overflows to trigger ADC
195 1 UART0_Init(); // Initialize UART0 for printf's
196 1 ADC0_Init(); // Initialize ADC0
197 1
198 1 EA = 1; // Enable global interrupts
199 1 while (1)
200 1 {
201 2 EA = 0; // Disable interrupts
202 2 printf("\f");
203 2 for(i = 0; i < ANALOG_INPUTS; i++)
204 2 {
205 3 // The 10-bit ADC value is averaged across INT_DEC measurements.
206 3 // The result is then stored in RESULT, and is right-justified
207 3 // The measured voltage applied to the port pins is then:
208 3 //
209 3 // Vref (mV)
210 3 // measurement (mV) = --------------- * Result (bits)
211 3 // (2^10)-1 (bits)
212 3
213 3 measurement = (RESULT[i] - 8) * 3268 / 1023;
214 3 printf("P1.%bu voltage: %4ld mV\n",PIN_TABLE[i],measurement);
215 3 }
216 2 EA = 1; // Re-enable interrupts
217 2
218 2 Timer0_wait(25); // Wait before displaying new values
219 2 }
220 1 }
221
222 //-----------------------------------------------------------------------------
223 // Initialization Subroutines
224 //-----------------------------------------------------------------------------
225
226 //-----------------------------------------------------------------------------
227 // SYSCLK_Init
228 //-----------------------------------------------------------------------------
229 //
230 // Return Value : None
231 // Parameters : None
232 //
233 // This routine initializes the system clock to use the internal 24.5MHz
234 // oscillator as its clock source. Also enables missing clock detector reset.
235 //
236 //-----------------------------------------------------------------------------
237 void Oscillator_Init (void)
238 {
239 1 OSCICN = 0x83; // Configure internal oscillator for
240 1 // its highest frequency
241 1 RSTSRC = 0x04; // Enable missing clock detector
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT_MUX 07/28/2008 14:50:43 PAGE 5
242 1 }
243
244 //-----------------------------------------------------------------------------
245 // Port_Init
246 //-----------------------------------------------------------------------------
247 //
248 // Return Value : None
249 // Parameters : None
250 //
251 // Configure the Crossbar and GPIO ports.
252 //
253 // P0.4 - UART TX (push-pull)
254 // P0.5 - UART RX
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