DS18B20 digital thermometer

Makefile

@@ -37,7 +37,8 @@ PROJECT = f030f4
 #SRCS = startup.c uplow.2.c hello.c
 #SRCS = startup.c clocks.c uptime.c
 #SRCS = startup.txeie.c txeie.c uptime.c
-SRCS = startup.txeie.c gpioa.c dht11main.c dht11.c
+#SRCS = startup.txeie.c gpioa.c dht11main.c dht11.c
+SRCS = startup.txeie.c gpioa.c ds18b20main.c ds18b20.c
 OBJS = $(SRCS:.c=.o)
 LIBOBJS = printf.o putchar.o puts.o
 CPU = -mthumb -mcpu=cortex-m0

ds18b20.c

@@ -0,0 +1,168 @@
+/* ds18b20.c -- 1-Wire digital thermometer */
+/* Copyright (c) 2020 Renaud Fivet */
+
+#include "ds18b20.h"    /* implements DS18B20 API */
+
+#include "system.h"     /* gpioa_(), usleep() */
+
+#define DIO 13
+#define input()     gpioa_input( DIO)
+#define output()    gpioa_output( DIO)
+#define bread()     gpioa_read( DIO)
+
+#define MAX_RETRIES 999
+#define wait_level( lvl) \
+    retries = MAX_RETRIES ; \
+    while( bread() != lvl) \
+        if( retries-- == 0) \
+            return DS18B20_FAIL_TOUT
+
+void ds18b20_init( void) {
+    input() ;           /* Wire floating, HIGH by pull-up */
+}
+
+static ds18b20_retv_t initialization() {
+/* Reset */
+    output() ;          /* Wire LOW */
+    usleep( 480) ;
+    input() ;           /* Wire floating, HIGH by pull-up */
+
+/* Presence */
+    int retries ;
+    wait_level( HIGH) ; /* Pull-up LOW -> HIGH, T1 */
+    wait_level( LOW) ;  /* DS18B20 asserts line to LOW, T2, T2 - T1 = 15~60us */
+    wait_level( HIGH) ; /* DS18B20 releases lines, Pull-up LOW -> HIGH, T3
+                        ** T3 - T2 = 60~240us */
+    usleep( 405) ;      /* 480 = 405 + 15 + 60 */
+
+    return DS18B20_SUCCESS ;
+}
+
+static void write( unsigned char uc) {
+/* Transmit byte, least significant bit first */
+    for( unsigned char curbit = 1 ; curbit ; curbit <<= 1) {
+    /* Transmit a bit takes 60us + 1us between transmit */
+    /* Write 1: <15us LOW */
+    /* Write 0:  60us LOW */
+        unsigned t = uc & curbit ? 13 : 60 ;
+        output() ;      /* Wire LOW */
+        usleep( t) ;
+        input() ;       /* Wire floating, HIGH by pull-up */
+        usleep( 61 - t) ;
+    }
+}
+
+static iolvl_t poll( void) {
+    output() ;  /* Wire LOW */
+    usleep( 1) ;
+    input() ;   /* Wire floating, HIGH by pull-up */
+    usleep( 5) ;
+    iolvl_t bit = bread() ;
+    usleep( 55) ;
+    return bit ;
+}
+
+static unsigned char read( unsigned char *p, int size) {
+    unsigned char crc = 0 ;
+
+    while( size--) {
+    /* Receive byte, least significant bit first */
+        unsigned char uc = 0 ;
+        for( unsigned char curbit = 1 ; curbit ; curbit <<= 1) {
+        /* read bit */
+            int v = poll() ;
+            if( v)
+                uc |= curbit ;
+
+        /* update CRC */
+            v ^= crc ;
+            crc >>= 1 ;
+            if( v & 1)
+                crc ^= 0x119 >> 1 ; /* reverse POLY = x^8 + x^5 + x^4 + 1 */
+        }
+
+    /* store byte */
+        *p++ = uc ;
+    }
+
+    return crc ;
+}
+
+static ds18b20_retv_t read_scratchpad( unsigned char scratchpad[]) {
+    ds18b20_retv_t ret = initialization() ;
+    if( ret != DS18B20_SUCCESS)
+        return ret ;
+
+    write( 0xCC) ;  /* Skip ROM */
+    write( 0xBE) ;  /* Read Scratchpad */
+    return read( scratchpad, 9) ? DS18B20_FAIL_CRC : DS18B20_SUCCESS ;
+}
+
+ds18b20_retv_t ds18b20_convert( void) {
+    ds18b20_retv_t ret ;
+
+    ret = initialization() ;
+    if( ret != DS18B20_SUCCESS)
+        return ret ;
+
+    write( 0xCC) ;  /* Skip ROM */
+    write( 0x44) ;  /* Convert T */
+    return DS18B20_SUCCESS ;
+}
+
+ds18b20_retv_t ds18b20_fetch( short *deciCtemp) { /* -550~1250 = -55.0~125.0 C */
+    ds18b20_retv_t ret ;
+    unsigned char vals[ 9] ;    /* scratchpad */
+
+    ret = read_scratchpad( vals) ;
+    if( ret != DS18B20_SUCCESS)
+        return ret ;
+
+    *deciCtemp = *((short *) vals) * 10 / 16 ;
+    return DS18B20_SUCCESS ;
+}
+
+ds18b20_retv_t ds18b20_read( short *deciCtemp) { /* -550~1250 = -55.0~125.0 C */
+    ds18b20_retv_t ret ;
+
+    ret = ds18b20_convert() ;
+    if( ret != DS18B20_SUCCESS)
+        return ret ;
+
+    do
+        usleep( 4000) ;
+    while( poll() == LOW) ; /* up to 93.75ms for 9 bits, 750ms for 12 bits */
+
+    return ds18b20_fetch( deciCtemp) ;
+}
+
+ds18b20_retv_t ds18b20_resolution( unsigned res) {  /* 9..12 bits  */
+    ds18b20_retv_t ret ;
+    unsigned char vals[ 9] ;    /* scratchpad */
+    unsigned char curres ;
+
+/* read scratchpad */
+    ret = read_scratchpad( vals) ;
+    if( ret != DS18B20_SUCCESS)
+        return ret ;
+
+/* update resolution if current value is different than requested */
+    res = (res - 9) & 3 ;
+    curres = vals[ 4] >> 5 ;
+    if( curres != res) {
+        vals[ 4] = (vals[ 4] & 0x1F) | (res << 5) ;
+        ret = initialization() ;
+        if( ret != DS18B20_SUCCESS)
+            return ret ;
+
+        write( 0xCC) ;  /* Skip ROM */
+        write( 0x4E) ;  /* Write Scratchpad */
+        write( vals[ 2]) ;
+        write( vals[ 3]) ;
+        write( vals[ 4]) ;
+    }
+
+    return DS18B20_SUCCESS ;
+}
+
+/* end of ds18b20.c */

ds18b20.h

@@ -0,0 +1,16 @@
+/* ds18b20.h -- 1-Wire temperature sensor */
+/* Copyright (c) 2020 Renaud Fivet */
+
+typedef enum {
+    DS18B20_SUCCESS,
+    DS18B20_FAIL_TOUT,
+    DS18B20_FAIL_CRC
+} ds18b20_retv_t ;
+
+void ds18b20_init( void) ;
+ds18b20_retv_t ds18b20_resolution( unsigned res) ;  /* 9..12 bits  */
+ds18b20_retv_t ds18b20_convert( void) ;
+ds18b20_retv_t ds18b20_fetch( short *deciCtemp) ;/* -550~1250 = -55.0~125.0 C */
+ds18b20_retv_t ds18b20_read( short *deciCtemp) ; /* -550~1250 = -55.0~125.0 C */
+
+/* end of ds18b20.h */

ds18b20main.c

@@ -0,0 +1,37 @@
+/* ds18b20main.c -- sample temperature using 1-Wire temperature sensor */
+/* Copyright (c) 2020 Renaud Fivet */
+
+#include <stdio.h>
+
+#include "system.h"     /* uptime */
+#include "ds18b20.h"    /* ds18b20_() */
+
+int main( void) {
+    unsigned last = 0 ;
+
+    ds18b20_init() ;
+    ds18b20_resolution( 12) ;   /* Set highest resolution: 12 bits */
+    ds18b20_convert() ;         /* start temperature conversion */
+    for( ;;)
+        if( last == uptime)
+            yield() ;
+        else {
+            short val ;
+
+            last = uptime ;
+            switch( ds18b20_fetch( &val)) {
+            case DS18B20_SUCCESS:
+                printf( "%i.%i\n", val / 10, val % 10) ;
+                break ;
+            case DS18B20_FAIL_TOUT:
+                puts( "Timeout") ;
+                break ;
+            case DS18B20_FAIL_CRC:
+                puts( "CRC Error") ;
+            }
+
+            ds18b20_convert() ; /* start temperature conversion */
+        }
+}
+
+/* end of ds18b20main.c */