write_multiple_registers: negative values

[Wizwalli]

Writing Negative Values with write_multiple_registers in Modbus INT16 for SOFAR HYD 20K 3PH

Hi everyone,

I’ve been using this repo to write positive values to my SOFAR HYD 20K 3PH inverter, which allows me to charge my battery on demand, utilizing either grid power or solar production, depending on availability. However, I’ve hit a roadblock when trying to discharge my battery.

The issue seems to stem from the way Modbus handles values, specifically the INT16 format, as described in this GitHub issue. My understanding is that INT16 limits the register values to represent signed integers, which makes writing negative values a challenge.

I’m curious if anyone else in the community has encountered this problem. If so, have you managed to find a workaround for writing negative values via write_multiple_registers? Any insights, solutions, or even just confirmation that this is a shared issue would be greatly appreciated!

Looking forward to hearing your thoughts.

[Wizwalli]

I'm still desperately looking for a way to solve this, nodered modbus seems like an option but bypasses the functionality that this integration offers.

Would highly appreciate if someone could share their thoughts 🙏

[davidrapan]

Hi @Wizwalli, did you try just setting the number w/ sign bit set to 1?

[Wizwalli]

Thanks for your feedback!

Are you suggesting passing positive numbers? That works well and functionally starts "charging" the battery.

Modbus User Guide Clarification

The Modbus User Guide (attached) states that register 1189 expects negative values for discharge.
SOFAR Modbus User Guide 2023-11-28.pdf

Debugging

Writing via developer tools

action: solarman.write_multiple_registers
data:
  device: guid
  register: 1189
  values: -200

Response

Failed to perform the action solarman.write_multiple_registers. value must be at least 0 @ data['values'][0]. Got None

Passing negatives via Node-RED:

{
   "device":"guid",
   "register":msg.hexAddress,
   "values":msg.value
}

Response

HomeAssistantError: value must be at least 0 @ data['values'][1]

[davidrapan]

No, I mean try for example write uint16 number 65408 which is -128 as int16.

[Wizwalli]

@davidrapan how do I pass the data representation type (unit16 vs int16) to the function write_multiple_registers?
I gave it a go without adding any data representation field and fieldvalue so I guess the function / modbus just interpreted the value as an int16

For example

{
   "device":"guid",
   "register":msg.hexAddress,
   "values":msg.value,
   "dataType":"uint16"
}

I believe this is the piece of logging that's resulted from it

2025-02-07 21:20:20.198 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] Call 10 ~ 4489 | 0x1189: [0, 65407, 0, 65407] ...
2025-02-07 21:20:20.198 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] SENT: a6 08 00 00 00 0f 01 10 11 89 00 04 08 00 00 ff 7f 00 00 ff 7f
2025-02-07 21:20:20.534 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] RECD: a6 08 00 00 00 14 01 10 11 89 00 04 15 1c 00 00 00 00 00 00 00 00 00 00 00 00
2025-02-07 21:20:20.534 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] Call 10 ~ 4489 | 0x1189: [0, 65407, 0, 65407] succeeded, response: 4
2025-02-07 21:20:23.518 DEBUG (MainThread) [custom_components.solarman.services] write_multiple_registers: <ServiceCall solarman.write_multiple_registers (c:01JKH145AYVYQZ17Z3Q2893GE0): device=675a2b89c2fd69ae5b4f315bc61455a9, register=4368, values=[0]>
2025-02-07 21:20:23.518 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] Scheduling request.
2025-02-07 21:20:23.518 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] Call 10 ~ 4368 | 0x1110: [0] ...
2025-02-07 21:20:23.518 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] SENT: 91 80 00 00 00 09 01 10 11 10 00 01 02 00 00
2025-02-07 21:20:23.850 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] RECD: 91 80 00 00 00 14 01 10 11 10 00 01 05 30 00 00 00 00 00 00 00 00 00 00 00 00
2025-02-07 21:20:23.851 DEBUG (MainThread) [custom_components.solarman.api] [2108379728] Call 10 ~ 4368 | 0x1110: [0] succeeded, response: 1

My inverter charging at max capacity :p

[davidrapan]

It's 32b and not 16b...

Can you set the register directly in your inverter to some negative number and then read it back again using built in ACTION for read? So i can see the order.