Ok, so despite what I quoted, I have the sensor now powered on 3.3V and I'm reading UART with no problem. I could swear that I tried powering it with 3.3V but it apparently was not the case. Lesson learned - if your UART is weird, check the power...
I still need to figure out how can I reset the serial buffer but that's another topic.
Thank you very much.
If someone will be interested here's my code (adapted from
here) working on an ESP-WROOM-32 DevKitC:
Code: Select all
import machine
import ustruct as struct
class PMS7003:
PMS_FRAME_LENGTH = 0
PMS_PM1_0 = 1
PMS_PM2_5 = 2
PMS_PM10_0 = 3
PMS_PM1_0_ATM = 4
PMS_PM2_5_ATM = 5
PMS_PM10_0_ATM = 6
PMS_PCNT_0_3 = 7
PMS_PCNT_0_5 = 8
PMS_PCNT_1_0 = 9
PMS_PCNT_2_5 = 10
PMS_PCNT_5_0 = 11
PMS_PCNT_10_0 = 12
PMS_VERSION = 13
PMS_ERROR = 14
PMS_CHECKSUM = 15
def get_uart(self):
uart = machine.UART(2, 9600)
uart.init(9600, bits=8, parity=None, stop=1)
return uart
def _assert_byte(self, byte, expected):
if byte is None or len(byte) < 1 or ord(byte) != expected:
return False
return True
def read(self):
uart = self.get_uart()
while True:
if not self._assert_byte(uart.read(1), 0x42):
print('bad first')
continue
if not self._assert_byte(uart.read(1), 0x4D):
print('bad second')
continue
read_buffer = uart.read(30)
if len(read_buffer) < 30:
continue
data = struct.unpack('!HHHHHHHHHHHHHBBH', read_buffer)
checksum = 0x42 + 0x4D
for c in read_buffer[0:28]:
checksum += c
if checksum != data[self.PMS_CHECKSUM]:
print('bad checksum')
continue
return {
'FRAME_LENGTH': data[self.PMS_FRAME_LENGTH],
'PM1_0': data[self.PMS_PM1_0],
'PM2_5': data[self.PMS_PM2_5],
'PM10_0': data[self.PMS_PM10_0],
'PM1_0_ATM': data[self.PMS_PM1_0_ATM],
'PM2_5_ATM': data[self.PMS_PM2_5_ATM],
'PM10_0_ATM': data[self.PMS_PM10_0_ATM],
'PCNT_0_3': data[self.PMS_PCNT_0_3],
'PCNT_0_5': data[self.PMS_PCNT_0_5],
'PCNT_1_0': data[self.PMS_PCNT_1_0],
'PCNT_2_5': data[self.PMS_PCNT_2_5],
'PCNT_5_0': data[self.PMS_PCNT_5_0],
'PCNT_10_0': data[self.PMS_PCNT_10_0],
'VERSION': data[self.PMS_VERSION],
'ERROR': data[self.PMS_ERROR],
'CHECKSUM': data[self.PMS_CHECKSUM],
}
pms = PMS7003()
while True:
pms_data = pms.read()
