?? f31x_adc0_externalinput.lst
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C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT 03/20/2009 15:55:34 PAGE 1
C51 COMPILER V8.08, COMPILATION OF MODULE F31X_ADC0_EXTERNALINPUT
OBJECT MODULE PLACED IN F31x_ADC0_ExternalInput.OBJ
COMPILER INVOKED BY: E:\Apps\Keil\C51\BIN\c51.exe F31x_ADC0_ExternalInput.c DB OE
line level source
1 //-----------------------------------------------------------------------------
2 // F31x_ADC0_ExternalInput.c
3 //-----------------------------------------------------------------------------
4 // Copyright 2006 Silicon Laboratories, Inc.
5 // http://www.silabs.com
6 //
7 // Program Description:
8 // --------------------
9 //
10 // This example code takes and averages 2048 analog measurements from input
11 // P2.5 using ADC0, then prints the results to a terminal window via the UART.
12 //
13 // The system is clocked by the internal 24.5MHz oscillator. Timer 2 triggers
14 // a conversion on ADC0 on each overflow. The completion of this conversion
15 // in turn triggers an interrupt service routine (ISR). The ISR averages
16 // 2048 measurements, then prints the value to the terminal via printf before
17 // starting another average cycle.
18 //
19 // The analog multiplexer selects P2.5 as the positive ADC0 input. This
20 // port is configured as an analog input in the port initialization routine.
21 // The negative ADC0 input is connected via mux to ground, which provides
22 // for a single-ended ADC input.
23 //
24 // A 100kohm potentiometer may be connected as a voltage divider between
25 // P0.0 and AGND on the terminal strip as shown below:
26 //
27 // ---------
28 // |
29 // |
30 // |
31 // o| P0.0 ----|
32 // o| GND ---|<-|
33 // o| |
34 // o| P2.5--------|
35 // |
36 //----------
37 // C8051F310-TB
38 //
39 // Note that the ADC reference voltage is tied to Vdd, not a precision
40 // internal reference. This limits the precision of the measurement,
41 // as Vdd is set by the regulator on the board, not the C8051F310.
42 //
43 // Terminal output is done via printf, which directs the characters to
44 // UART0. A UART initialization routine is therefore necessary.
45 //
46 // ADC Settling Time Requirements, Sampling Rate:
47 // ----------------------------------------------
48 //
49 // The total sample time per input is comprised of an input setting time
50 // (Tsettle), followed by a conversion time (Tconvert):
51 //
52 // Tsample = Tsettle + Tconvert
53 //
54 // |--------Settling-------|==Conversion==|----Settling--- . . .
55 // Timer 2 overflow ^
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT 03/20/2009 15:55:34 PAGE 2
56 // ADC0 ISR ^
57 //
58 // The ADC input voltage must be allowed adequate time to settle before the
59 // conversion is made. This settling depends on the external source
60 // impedance, internal mux impedance, and internal capacitance.
61 // Settling time is given by:
62 //
63 // | 2^n |
64 // Tsettle = ln | --- | * Rtotal * Csample
65 // | SA |
66 //
67 // In this application, assume a 100kohm potentiometer as the voltage divider.
68 // The expression evaluates to:
69 //
70 // | 2^10 |
71 // Tsettle = ln | ---- | * 105e3 * 5e-12 = 4.4uS
72 // | 0.25 |
73 //
74 // In addition, one must allow at least 1.5uS after changing analog mux
75 // inputs or PGA settings. The settling time in this example, then, is
76 // dictated by the large external source resistance.
77 //
78 // The conversion is 10 periods of the SAR clock <SAR_CLK>. At 3 MHz,
79 // this time is 10 * 400nS = 3.3 uS.
80 //
81 //
82 // Tsample, minimum = Tsettle + Tconvert
83 // = 4.4uS + 3.3uS
84 // = 7.7 uS
85 //
86 // Timer 2 is set to start a conversion every 100uS, which is far longer
87 // than the minimum required.
88 //
89 // F310 Resources:
90 // ---------------
91 // Timer1: clocks UART
92 // Timer2: overflow initiates ADC conversion
93 //
94 // How To Test:
95 // ------------
96 // 1) Download code to a 'F310 device on a C8051F310-TB development board
97 // 2) Connect serial cable from the transceiver to a PC
98 // 3) On the PC, open HyperTerminal (or any other terminal program) and connect
99 // to the COM port at <BAUDRATE> and 8-N-1
100 // 4) Connect a variable voltage source (between 0 and VDD)
101 // to P2.5, or a potentiometer voltage divider as shown above.
102 // 5) HyperTerminal will print the voltage measured by the device if
103 // everything is working properly
104 //
105 // FID: 31X000011
106 // Target: C8051F310
107 // Tool chain: Keil C51 7.50 / Keil EVAL C51
108 // Command Line: None
109 //
110 //
111 // Release 1.0
112 // -Initial Revision (clm)
113 // -24-Jul-06
114
115
116 //-----------------------------------------------------------------------------
117 // Includes
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT 03/20/2009 15:55:34 PAGE 3
118 //-----------------------------------------------------------------------------
119 #include "c8051F310.h" // SFR declarations
120 #include <stdio.h>
121
122 //-----------------------------------------------------------------------------
123 // 16-bit SFR Definitions for 'F31x
124 //-----------------------------------------------------------------------------
125
126 sfr16 TMR2RL = 0xca; // Timer2 reload value
127 sfr16 TMR2 = 0xcc; // Timer2 counter
128 sfr16 ADC0 = 0xbd; // ADC0 result
129
130 //-----------------------------------------------------------------------------
131 // Global CONSTANTS
132 //-----------------------------------------------------------------------------
133
134 #define SYSCLK 24500000 // SYSCLK frequency in Hz
135 #define BAUDRATE 115200 // Baud rate of UART in bps
136
137 sbit LED = P3^3; // LED='1' means ON
138
139 //-----------------------------------------------------------------------------
140 // Function PROTOTYPES
141 //-----------------------------------------------------------------------------
142 void SYSCLK_Init (void);
143 void PORT_Init (void);
144 void Timer2_Init(void);
145 void ADC0_Init(void);
146 void UART0_Init (void);
147
148
149 void ADC_Init()
150 {
151 1 int SARCLK=3000000; // 3 Mhz
152 1 // Use AD0BUSY as conversion enable
153 1 ADC0CN=0x40; // ADC with normal track mode
154 1 //REF0CN=0x0e; // Enable temp sensor and use on chip Vref (VDD)
155 1 // REF0CN=0x0A; // Enable temp sensor and use on external Vref
156 1 AMX0N=0x1F; // Single-Ended inputs
157 1 ADC0CF=(SYSCLK/SARCLK-1)<<3; // Conversion clock setting & results are right-justified
158 1 ADC0CF |= 0x00; // right-justify results
159 1 EIE1 &= 0xF1; // Disable ADC interrupt & disable win compare interrupts
160 1 AD0EN=1; // Enable ADC, ready for data conversion
161 1 }
162
163 unsigned int ADC_Read_Ch(unsigned char chan_num)
164 {
165 1 unsigned long result;
166 1 static int measure = 2048;
167 1 static unsigned long accumulator = 0;
168 1 unsigned long mV; // measured voltage in mV
169 1
170 1
171 1
172 1 AMX0P = chan_num; // Select chan to be read thru the MUX
173 1 AD0INT = 0; // Clear conversion complete indicator
174 1 AD0BUSY = 1; // Initiate conversion
175 1
176 1 while (!AD0INT); // Wait for convesion completed.
177 1
178 1
179 1
C51 COMPILER V8.08 F31X_ADC0_EXTERNALINPUT 03/20/2009 15:55:34 PAGE 4
180 1 result = ADC0H; // Stuff converted data
181 1 result = (result << 8) | ADC0L;
182 1
183 1
184 1 accumulator += result;
185 1 measure--;
186 1
187 1 if(measure == 0)
188 1 {
189 2 measure = 2048;
190 2 result = accumulator / 2048;
191 2 accumulator=0;
192 2
193 2 // The 10-bit ADC value is averaged across 2048 measurements.
194 2 // The measured voltage applied to P1.4 is then:
195 2 //
196 2 // Vref (mV)
197 2 // measurement (mV) = --------------- * result (bits)
198 2 // (2^10)-1 (bits)
199 2
200 2 mV = result * 3250 / 1023;
201 2 printf("P3.1 voltage: %ld mV\n",mV);
202 2 }
203 1
204 1
205 1
206 1 return result;
207 1 }
208
209 //-----------------------------------------------------------------------------
210 // MAIN Routine
211 //-----------------------------------------------------------------------------
212 void main (void)
213 {
214 1 PCA0MD &= ~0x40; // WDTE = 0 (clear watchdog timer
215 1 // enable)
216 1
217 1 SYSCLK_Init (); // Initialize system clock to
218 1 // 12MHz
219 1 PORT_Init (); // Initialize crossbar and GPIO
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