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ds18b20: Allow some read errors 

Allows a limited number of DS18B20 read failures
before stopping the printer. This is designed to
tolerate spurious read errors, while still stopping
for serious issues.

The printer will stop when the sensor

fails to report a value five times in a row.

Implementation works as follows:
The MCU reports any read errors using a new "fault"
parameter in its answers.
The Python code tracks the number of errors
and triggers the shutdown. This paves the way for
more sophisticated error handling in the future,
as well as an example for other sensors to follow.

Signed-off-by: Lorenzo Pfeifer <Lorenzo.Pfeifer+github@googlemail.com>
This commit is contained in:
functionpointer 2022-06-05 14:26:51 +02:00 committed by Kevin O'Connor
parent b0da191bee
commit 2dc20c011d
2 changed files with 38 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
klippy/extras/ds18b20.py
View File

@ -10,6 +10,7 @@ DS18_REPORT_TIME = 3.0
# Temperature can be sampled at any time but conversion time is ~750ms, so
# setting the time too low will not make the reports come faster.
DS18_MIN_REPORT_TIME = 1.0
DS18_MAX_CONSECUTIVE_ERRORS = 4
class DS18B20:
def __init__(self, config):
@ -32,7 +33,7 @@ class DS18B20:
def _build_config(self):
sid = "".join(["%02x" % (x,) for x in self.sensor_id])
self._mcu.add_config_cmd("config_ds18b20 oid=%d serial=%s"
% (self.oid, sid))
% (self.oid, sid, DS18_MAX_CONSECUTIVE_ERRORS))
clock = self._mcu.get_query_slot(self.oid)
self._report_clock = self._mcu.seconds_to_clock(self.report_time)
@ -44,7 +45,9 @@ class DS18B20:
def _handle_ds18b20_response(self, params):
temp = params['value'] / 1000.0
if temp < self.min_temp or temp > self.max_temp:
if params["fault"] != 0:
temp = 0 # read error! report 0C and don't check temp range
elif temp < self.min_temp or temp > self.max_temp:
self.printer.invoke_shutdown(
"DS18B20 temperature %0.1f outside range of %0.1f:%.01f"
% (temp, self.min_temp, self.max_temp))

55
src/linux/sensor_ds18b20.c
View File

@ -13,7 +13,6 @@
#include <time.h> // clock_gettime
#include "basecmd.h" // oid_alloc
#include "board/irq.h" // irq_disable
#include "board/misc.h" // output
#include "command.h" // DECL_COMMAND
#include "internal.h" // report_errno
#include "sched.h" // DECL_SHUTDOWN
@ -51,17 +50,23 @@ struct ds18_s {
int temperature;
struct timespec request_time;
uint8_t status;
const char* error;
uint8_t error_count;
uint8_t max_error_count;
};
// Lock ds18_s mutex, set error status and message, unlock mutex.
// Lock ds18_s mutex, set error status, unlock mutex.
static void
locking_set_read_error(struct ds18_s *d, const char *error)
locking_handle_read_error(struct ds18_s *d)
{
pthread_mutex_lock(&d->lock);
d->error = error;
d->status = W1_ERROR;
pthread_mutex_unlock(&d->lock);
d->error_count++;
if (d->error_count <= d->max_error_count) {
pthread_mutex_unlock(&d->lock);
} else {
pthread_mutex_unlock(&d->lock);
pthread_exit(NULL);
}
}
// The kernel interface to DS18B20 sensors is a sysfs entry that blocks for
@ -89,15 +94,14 @@ reader_start_routine(void *param) {
int ret = read(d->fd, data, sizeof(data)-1);
if (ret < 0) {
report_errno("read DS18B20", ret);
locking_set_read_error(d, "Unable to read DS18B20");
pthread_exit(NULL);
locking_handle_read_error(d);
continue;
}
data[ret] = '\0';
char *temp_string = strstr(data, "t=");
if (temp_string == NULL || temp_string[2] == '\0') {
locking_set_read_error(d,
"Unable to find temperature value in DS18B20 report");
pthread_exit(NULL);
locking_handle_read_error(d);
continue;
}
// Don't pass 't' and '=' to atoi
temp_string += 2;
@ -113,8 +117,8 @@ reader_start_routine(void *param) {
ret = lseek(d->fd, 0, SEEK_SET);
if (ret < 0) {
report_errno("seek DS18B20", ret);
locking_set_read_error(d, "Unable to seek DS18B20");
pthread_exit(NULL);
locking_handle_read_error(d);
continue;
}
}
pthread_exit(NULL);
@ -151,6 +155,8 @@ command_config_ds18b20(uint32_t *args)
}
struct ds18_s *d = oid_alloc(args[0], command_config_ds18b20, sizeof(*d));
d->max_error_count = args[3];
d->error_count = 0;
d->timer.func = ds18_event;
d->fd = fd;
d->status = W1_IDLE;
@ -181,7 +187,8 @@ fail4:
fail5:
shutdown("Could not start DS18B20 reader thread");
}
DECL_COMMAND(command_config_ds18b20, "config_ds18b20 oid=%c serial=%*s");
DECL_COMMAND(command_config_ds18b20,
"config_ds18b20 oid=%c serial=%*s max_error_count=%c");
void
command_query_ds18b20(uint32_t *args)
@ -215,12 +222,15 @@ ds18_send_and_request(struct ds18_s *d, uint32_t next_begin_time, uint8_t oid)
pthread_mutex_lock(&d->lock);
if (d->status == W1_ERROR) {
// try_shutdown expects a static string. Output the specific error,
// then shut down with a generic error.
output("Error: %s", d->error);
pthread_mutex_unlock(&d->lock);
try_shutdown("Error reading DS18B20 sensor");
return;
if (d->error_count > d->max_error_count) {
try_shutdown("Error reading DS18B20 sensor");
pthread_mutex_unlock(&d->lock);
return;
} else {
sendf("ds18b20_result oid=%c next_clock=%u value=%i fault=%u"
, oid, next_begin_time, d->temperature, d->error_count);
d->status = W1_READ_REQUESTED;
}
} else if (d->status == W1_IDLE) {
// This happens the first time requesting a temperature.
// Nothing to report yet.
@ -228,8 +238,8 @@ ds18_send_and_request(struct ds18_s *d, uint32_t next_begin_time, uint8_t oid)
d->status = W1_READ_REQUESTED;
} else if (d->status == W1_READY) {
// Report the previous temperature and request a new one.
sendf("ds18b20_result oid=%c next_clock=%u value=%i"
, oid, next_begin_time, d->temperature);
sendf("ds18b20_result oid=%c next_clock=%u value=%i fault=%u"
, oid, next_begin_time, d->temperature, 0);
if (d->temperature < d->min_value || d->temperature > d->max_value) {
pthread_mutex_unlock(&d->lock);
try_shutdown("DS18B20 out of range");
@ -237,6 +247,7 @@ ds18_send_and_request(struct ds18_s *d, uint32_t next_begin_time, uint8_t oid)
}
d->request_time = request_time;
d->status = W1_READ_REQUESTED;
d->error_count = 0; //successful reading, reset error count
} else if (d->status == W1_READ_REQUESTED) {
// Reader thread is already reading (or will be soon).
// This can happen if two queries come in quick enough