Why do glblelctl and glblazctl always read zero?

Zero is a valid scaled value. Apply the dgr_sf scale factor before interpreting angle registers. If dgr_sf is -1, a raw value of 450 means 45.0 degrees. Check the scale factor register first; zero raw plus any negative scale factor still yields zero, which may be correct at night when a stow position of 0 degrees is commanded.

The gateway connects but the id register returns unexpected values. What now?

SunSpec model blocks are not always at a fixed absolute address. Model 601 is located by walking the SunSpec device map from the well-known base address. Confirm the template base address matches where model 601 actually sits in your controller's map by reading the id register at the configured offset and checking it equals 601.

Is it safe to write to glblelctl, glblazctl, or glblctl remotely?

Writing to these registers overrides the controller's automatic sun-tracking algorithm for all trackers simultaneously. An incorrect elevation or azimuth setpoint can drive panels into stow conflicts, mechanical limits, or shading rows. Always verify the control mode in glblctl, test with a small angle offset during low-wind conditions, and confirm with your tracker manufacturer whether remote writes require a local-override interlock.

Modbus TCP connection is refused on port 502. How do I fix this?

Most tracker controllers ship with Modbus TCP disabled by default. Enable it in the communication section of the controller's web or HMI interface. Also confirm there is no firewall or VLAN rule blocking TCP 502 between the ModbusCloud Gateway and the controller's IP address, and that no other Modbus client is holding the single available TCP connection.

Free Modbus template: SunSpec Model 601 — Tracker Controller DRAFT 2

Name: SunSpec Model 601 — Tracker Controller DRAFT 2
Brand: SunSpec
SKU: 166f8400-7d8f-4762-aabc-43d2bc9bb56b

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Free Modbus template: SunSpec Model 601 — Tracker Controller DRAFT 2 | ModbusCloud

Registers (13)

13 read / 3 write

Name	Address	Function	Type	Unit	Access
id SunSpec model identifier, fixed value 601 for Tracker Controller.	0	FC03	uint16		R
l Length of this model block in 16-bit registers.	1	FC03	uint16		R
nam Controller name string, up to 8 registers of ASCII text.	2	FC03	string		R
typ Tracker type enumeration, identifies single-axis or dual-axis variant.	10	FC03	uint16		R
dtloc Local date at the controller, formatted YYYYMMDD.	11	FC03	string	YYYYMMDD	R
tmloc Local time at the controller, formatted hhmmss.	16	FC03	string	hhmmss	R
day Day-of-week value reported by the controller clock.	19	FC03	uint16		R
glblelctl Global elevation angle setpoint in degrees, writable to all trackers.	20	FC03	int32	Degrees	R/W
glblazctl Global azimuth angle setpoint in degrees, writable to all trackers.	22	FC03	int32	Degrees	R/W
glblctl Global control mode word, selects automatic or manual override mode.	24	FC03	uint16		R/W
glblalm Global alarm flag, true when any tracker reports a fault condition.	25	FC03	bool		R
dgr_sf Scale factor applied to degree values, expressed as a power of ten.	26	FC03	int16		R
n Number of individual tracker repeating blocks that follow in this model.	27	FC03	uint16		R