ADC calibration application to experiment with the internal temperature sensor using a DS18B20 as reference.

Makefile

@@ -39,7 +39,8 @@ PROJECT = f030f4
 #SRCS = startup.txeie.c txeie.c uptime.c
 #SRCS = startup.txeie.c gpioa.c dht11main.c dht11.c
 #SRCS = startup.txeie.c gpioa.c ds18b20main.c ds18b20.c
-SRCS = startup.txeie.c adc.c adcmain.c
+#SRCS = startup.txeie.c adc.c adcmain.c
+SRCS = startup.txeie.c adc.c adccalib.c ds18b20.c
 OBJS = $(SRCS:.c=.o)
 LIBOBJS = printf.o putchar.o puts.o
 CPU = -mthumb -mcpu=cortex-m0

adccalib.c

@@ -0,0 +1,77 @@
+/* adccalib.c -- ADC calibration of internal temperature sensor */
+/* Copyright (c) 2020-2021 Renaud Fivet */
+
+#include <stdio.h>
+#include "system.h"     /* uptime, adc_vnt() */
+#include "ds18b20.h"    /* ds18b20_() */
+
+#define ABS( i) ((i < 0) ? -i : i)
+
+static void track( short *minp, short *maxp, short val) {
+    if( val < *minp)
+        *minp = val ;
+
+    if( val > *maxp)
+        *maxp = val ;
+}
+
+int main( void) {
+    unsigned last = 0 ;
+    short calV, calC ;
+    short minC, maxC ;  /* Track temperature from DS18B20 */
+    short minV, maxV ;  /* Track ADC raw Vref */
+    short minT, maxT ;  /* Track ADC raw Tsense */
+
+    minC = minV = minT = 0x7FFF ;
+    maxC = maxV = maxT = -32768 ;
+
+/* Initialize ADC and fetch calibration values */
+    adc_vnt( VNT_INIT, &calV, &calC) ;
+    printf( "%u, %u\n", calV, calC) ;
+    int tconst = 6660 * calV / calC ;
+
+/* Initialize DS18B20 and initiate temperature conversion */
+    ds18b20_init() ;
+    ds18b20_resolution( 12) ;   /* Set highest resolution: 12 bits */
+    ds18b20_convert() ;         /* start temperature conversion */
+
+/* main acquisition loop, reads samples every seconds */
+    for( ;;)
+        if( uptime == last)
+            yield() ;
+        else {
+            short Vsample, Csample ;
+
+            last = uptime ;
+
+        /* Track DS18B20 temperature readings */
+            switch( ds18b20_fetch( &Csample)) {
+            case DS18B20_SUCCESS:
+                track( &minC, &maxC, Csample) ;
+                printf( "%i.%i, %i, %i, ", Csample / 10, ABS( Csample % 10),
+                                                                minC, maxC) ;
+                break ;
+            case DS18B20_FAIL_TOUT:
+                printf( "Timeout, ") ;
+                break ;
+            case DS18B20_FAIL_CRC:
+                printf( "CRC Error, ") ;
+            }
+
+            ds18b20_convert() ; /* start temperature conversion */
+
+        /* Track Internal Temperature Sensor readings */
+            adc_vnt( VNT_RAW, &Vsample, &Csample) ;
+            track( &minV, &maxV, Vsample) ;
+            track( &minT, &maxT, Csample) ;
+            printf( "%i, %i, %i, %i, %i, %i, %i, %i, ",
+                    calV, Vsample, minV, maxV,
+                    calC, Csample, minT, maxT) ;
+            Csample = 3630 - (1 + tconst * Csample / Vsample) / 2 ;
+            Vsample = (660 * calV / Vsample + 1) / 2 ;
+            printf( "%i.%i, %i.%i\n",   Vsample / 100, ABS( Vsample % 100),
+                                        Csample / 10, ABS( Csample % 10)) ;
+        }
+}
+
+/* end of adccalib.c */