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mhz19: cleanup uart RX buffer before sending command

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When sensor is connected to hardware uart, sometimes on boot
uart's RX buffer contains several bytes of junk. Workaround it
by draining all of it before sending command.
Also turn on cleanup logic only if problem is detected (i.e.
when reply from sensor doesn't look correct.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
This commit is contained in:
Igor Mammedov 2019-05-05 21:58:01 +02:00 committed by nur
parent 62e57aeac3
commit a78a98bef5
1 changed files with 33 additions and 14 deletions
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47
esphome/components/mhz19/mhz19.cpp
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@ -52,23 +52,42 @@ void MHZ19Component::update() {
}
bool MHZ19Component::mhz19_write_command_(const uint8_t *command, uint8_t *response) {
ESP_LOGD(TAG, "cmd [%s]", dump_data_buf(command));
this->write_array(command, MHZ19_PDU_LENGTH);
this->flush();
bool ret;
int rx_error = 0;
if (response == nullptr)
return true;
do {
ESP_LOGD(TAG, "cmd [%s]", dump_data_buf(command));
this->write_array(command, MHZ19_PDU_LENGTH);
this->flush();
bool ret = this->read_array(response, MHZ19_PDU_LENGTH);
ESP_LOGD(TAG, "resp [%s]", dump_data_buf(response));
if (response == nullptr)
return true;
uint8_t checksum = mhz19_checksum(response);
if (checksum != response[8]) {
ESP_LOGW(TAG, "MHZ19 Checksum doesn't match: 0x%02X!=0x%02X [%s]",
response[8], checksum, dump_data_buf(response));
this->status_set_warning();
return false;
}
memset(response, 0, MHZ19_PDU_LENGTH);
ret = this->read_array(response, MHZ19_PDU_LENGTH);
ESP_LOGD(TAG, "resp [%s]", dump_data_buf(response));
uint8_t checksum = mhz19_checksum(response);
if (checksum != response[8]) {
ESP_LOGW(TAG, "MHZ19 Checksum doesn't match: 0x%02X!=0x%02X [%s]",
response[8], checksum, dump_data_buf(response));
/*
* UART0 in NodeMCU v2, sometimes on boot has junk in RX buffer,
* check for it and drain all of it before sending commands to sensor
*/
this->drain();
ret = false;
if (++rx_error > 2) {
this->status_set_warning();
/* give up trying to recover, hope that it will be fine next update cycle */
rx_error = 0;
}
delay(100);
} else {
rx_error = 0;
}
} while (rx_error);
return ret;
}