Regin Regio Midi controller

Register map(s) for this device, with a note of how far each has been checked. Addresses are 0-based, as on the wire. Scale and byte order are confirmed only at the hardware-verified rung.

coherence-checked

Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.

point	address (0-based)	type	scale	unit
rc_actual_x_regio_fan_switch	5	U16	1
rc_actual_x_regio_unit_state	6	U16	1	%
rc_actual_x_regio_controller_state	7	U16	1	%
rc_actual_x_regio_fan_speed	8	U16	1	%
rc_actual_r_regio_room_temp	10	I16	0.1
rc_actual_r_regio_room_temp_ext	11	I16	0.1
rc_actual_r_regio_room_temp_int	12	I16	0.1
rc_actual_r_regio_ai_change_over	13	I16	0.1
rc_actual_r_regio_ana_in1	14	I16	0.1
rc_actual_r_regio_u_ana_in1	15	I16	1
rc_actual_r_regio_set_p_adjustment	18	I16	0.1
rc_actual_r_regio_pid_set_p	19	I16	0.1
rc_actual_r_regio_pid_output	20	I16	1	%
rc_actual_r_regio_heat_output	21	I16	1	%
rc_actual_r_regio_cool_output	22	I16	1	%
rc_actual_r_regio_room_co2	31	I16	1	ppm
rc_actual_r_regio_volt_input	44	I16	0.1	V
rc_actual_r_regio_room_flow	45	I16	0.1	ms
rc_actual_r_regio_supply_air_temp	46	I16	0.1	ms
rc_setp_x_regio_fan_select	4	U16	1
rc_setp_r_regio_occ_set_p_heat	67	I16	0.1	°C
rc_setp_r_regio_occ_set_p_cool	68	I16	0.1	°C
rc_setp_r_regio_standby_set_p_dead_band	69	I16	0.1	°C
rc_setp_r_regio_un_occ_set_p_heat	70	I16	0.1	°C
rc_setp_r_regio_un_occ_set_p_cool	71	I16	0.1	°C
rc_setp_r_regio_frost_set_p	72	I16	0.1	°C
rc_setp_r_regio_setpoint_offset_pos	73	I16	0.1	°C
rc_setp_r_regio_setpoint_offset_neg	74	I16	0.1	°C
rc_setp_r_regio_set_p_offset	75	I16	0.1	°C

link settings as documented (unverified): RTU; FC 01,02,03,04,05,06,15,16; The Midi controller automatically switches between EXOline and Modbus depending on the present communication type, without any communication error.

bench facts as documented (unverified)

terminals	A and B, protective earth (N)
A/B polarity	A -> A and B -> B. Incorrect polarity will just give nonfunction but cannot harm either unit.
shield/ground	protective earth (N on EXO controllers)
response timeout	5 ms
inter-frame delay	3 ms
model register	Input Register 1
firmware register	Input Register 5
power	24 V AC
doc revision	Revision B, 2018-02-16

field reports — community-sourced, unverified (checked 2026-06-11)

BACnet support was mistakenly activated in models without display (RC-C3, RC-C3H, RC-C3O, RC-CF, RCCT, RC-CTO, RC-CTH, RCC-C3HCS), which could cause an irreversible change in protocol from Modbus/EXOline to BACnet. This was fixed in firmware version 1.7.1-04. [source]
Pymodbus RTU sync issue with consecutive readings/writings on Regin hardware, where consecutive requests frequently fail due to incomplete messages received. [source]
confirmed: The Midi controller automatically switches between EXOline and Modbus depending on the present communication type, without any communication error. — confirmed by Regin Regio Midi Manual (Chapter 16 Modbus signal types) [1.1.2]
confirmed: Modbus RTU framing, Even parity, 1 stop bit, and function codes 1, 2, 3, 4, 5, 6, 15, 16 — confirmed by Regin Regio Midi Manual
confirmed: RS485 polarity A -> A and B -> B, incorrect polarity will just give nonfunction but cannot harm either unit — confirmed by Regin Regio Midi Manual
confirmed: Modbus timeout for character (t1.5) default is 3 ms, and Modbus answer delay (t3.5) default is 5 ms — confirmed by Regin Regio Midi Manual (RC_Setp_X.RegioModbusCharTimeout and RC_Setp_X.RegioModbusAnswerDelay)
confirmed: Register map addresses (e.g., rc_actual_x_regio_fan_switch @ 5, rc_actual_r_regio_room_temp @ 10, rc_setp_r_regio_occ_set_p_heat @ 67) — confirmed by Regin Regio Midi Variable List (0-based mapping matches the 1-based Modbus addresses 6, 11, and 68 respectively)

The trust ladder

Each rung states what it proved and what it did not. Gray until proven; green is earned by hardware only.

generated — A prompt produced it. Unproven — anyone can regenerate this.
structure-verified — Decode path is structurally sound (addresses, widths, finite values). Does NOT prove word order or scaling.
coherence-checked — Round-trips through a real Modbus stack with no overlapping addresses and a word-order-sensitive codec — the map is internally coherent and wire-decodable. Does NOT prove byte-order or scaling match a real device: the emulator is seeded from the map's own types, so a uniformly wrong byte-order still round-trips. Only hardware-verified confirms byte-order/scale on the wire.
hardware-verified (software-key) x1 — Matched a real device with operator-attested readings as ground truth — the only rung that confirms word order + scaling on the wire.

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