Growatt Inverter Monitoring

growatt.py

#! /usr/bin/python3
# James Fraser <fwaggle@fwaggle.org>
# Released under the WTFPL.

# Repeatedly ask a Growatt inverter to spam us with updates.
# When it does so, collect them up, average them out, and
# every ten seconds send the average to a collectd server.

import collectd
import serial
import time

inverter = None
collectd.start_threads()
conn = collectd.Connection(hostname='s0lar.home.fwaggle.org', collectd_host='192.168.0.2')

def inverter_init():
	global inverter
	print("Initializing inverter")
	if not inverter or not inverter.is_open:
		inverter = serial.Serial('/dev/ttyu0', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=1)

	# This is *supposed* to ask the inverter to delay for 1000ms between
	# updates. My inverter 100% does not, it sends updates as fast as it
	# can, which amounts to about 5Hz.
	inverter.write(b'\x3F\x23\x7E\x34\x41\x7E\x32\x59\x31\x30\x30\x30\x23\x3F')
	inverter.write(b'\x3F\x23\x7E\x34\x42\x7E\x23\x3F')

def handle_packet(packet):
	# Sanity checks...
	if packet[30] != 0x57:
		print("Did not find next data packet start, expected 57 got %s" % (hex(packet[30])))
		return False

	# struct.unpack is for nerds
	PV1 = 0.1 * ((packet[0] << 8) + packet[1])
	PV2 = 0.1 * ((packet[4] << 8) + packet[5])
	grid_v = 0.1 * ((packet[6] << 8) + packet[7])
	grid_hz = 0.01 * ((packet[8] << 8) + packet[9])
	power = 0.1 * ((packet[10] << 8) + packet[11])
	temp = 0.1 * ((packet[12] << 8) + packet[13])
	status = (packet[14])
	fault = (packet[15])
	today = 0.1 * ((packet[20] << 8) + packet[21])

	# More Sanity checks
	if status not in [0, 1, 2]:
		raise Exception("Invalid status found, expecting 0, 1, or 2, got %d" % status)
		

	if status != 1 and power > 0:
		raise Exception("Status is a failure and power is non-zero, probably garbage. Status: %d Power: %.1f" % (status, power))

	#print("PV1: %.1f  PV2: %.1f" % (PV1, PV2))
	#print("Grid: %.1fV @ %.2fHz" % (grid_v, grid_hz))
	#print("Power: %.1fW" % (power))
	#print("Temperature: %.1fC" % (temp))
	#print("Today: %.1fkWh" % (today))

	return (power, grid_v, today)

def main():
	running = False
	hunting = True
	data_packet = bytearray(31)
	idle = 0
	last_time = 0
	power_readings = []
	while True:
		# If we're not running, send the init packet and then start hunting
		if not running:
			inverter_init()
			running = True
			hunting = True
			idle = 0

		# If we've had 5 timeouts, wait 30 seconds, then try re-init.
		if idle > 5:
			running = False
			time.sleep(30)
			continue

		# hunt for 0x57, which is the "start of response packet" (but may not be)
		while hunting:
			res = inverter.read()
			if res == b'':
				time.sleep(1)
				idle = idle + 1
				break

			if res == b'\x57':
				hunting = False
				break

		# If we're hunting, don't try read 31 bytes.
		if hunting:
			continue

		# If we get here, the inverter is spamming us with data, so let's record it.
		bread = inverter.readinto(data_packet)
		if bread != 31:
			print("Got %d bytes, expected 31..." % bread)
			hunting = True
		else:
			try:
				(power, grid_v, today) = handle_packet(data_packet)
				power_readings.append(power)
				now = time.time()

				if now - 10 > last_time:
					power_current = sum(power_readings) / len(power_readings)
					conn.growatt.set_exact(power = power_current)
					print("Power: %.1f (%d readings) Today: %.1f" % (power_current, len(power_readings), today))
					power_readings = list()
					last_time = now

			except Exception as e:
				print(str(e))
				hunting = True

main()