# ModBus Error Message - "CNC Error"

**URL:** <https://forum.onefinitycnc.com/t/modbus-error-message-cnc-error/14938>\
**Category:** Uncategorized\
**Created:** [August 29, 2022, 5:00am UTC](https://forum.onefinitycnc.com/t/modbus-error-message-cnc-error/14938 "2022-08-29T05:00:11Z")\
**Posts on this page:** 1\
**Showing post:** 6

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**Author:** ![349iq2345](https://avatars.discourse-cdn.com/v4/letter/3/bb73d2/32.png) [@349iq2345](https://forum.onefinitycnc.com/u/349iq2345)\
**Post date:** [August 30, 2022, 6:30am UTC](https://forum.onefinitycnc.com/t/modbus-error-message-cnc-error/14938/6 "2022-08-30T06:30:55Z")

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Hey Lowkey,

are you sure you don’t mean “CRC Error” instead of “CNC Error”? There exists no such error [in the source code](https://github.com/OneFinityCNC/onefinity-firmware). But if you have [CRC Errors](https://en.wikipedia.org/wiki/Cyclic_redundancy_check), this does mean that the data on your serial line get corrupted. I would strongly recommend to check your wire and its connections.

Note that [single strand wire](https://en.wikipedia.org/wiki/Copper_conductor#Solid_and_stranded) is for permanent, fixed installation only and not suitable for applications where movement is expected (for example, if the cable hangs freely and could be bumped, or if there is still trial and error with the positioning of the components of the installation, or if the machine is occasionally disassembled. Also, single strand wires should always be secured to the underlying surface with nail clamps). Better use [twisted pair](https://en.wikipedia.org/wiki/Twisted_pair), [shielded](https://en.wikipedia.org/wiki/Shielded_cable), [stranded wire](https://en.wikipedia.org/wiki/Wire#Stranded) with cross-sectional area according to your VFD manual (e.g. 0.14–0.75 [mm²](https://en.wikipedia.org/wiki/IEC_60228) / 28–14 [AWG](https://en.wikipedia.org/wiki/American_wire_gauge)) with matching [wire ferrules](https://en.wikipedia.org/wiki/Electric_wire_ferrule) and correct wire ferrule crimp pliers (e.g. [wire ferrule crimping pliers from Knipex](https://www.knipex.com/search?keys=wire+ferrules+crimping+pliers) or [crimping die for insulated and non-insulated wire ferrules](https://www.knipex.com/products/crimping-pliers/crimping-dies-for-knipex-crimp-system-pliers-art-no-97-43-xx/crimping-diesfor-knipex-crimp-system-pliers-art-no-xx/974908) for the [Crimp System Pliers for exchangeable crimping dies (version with case)](https://www.knipex.com/products/crimping-pliers/crimp-system-pliers-for-exchangeable-crimping-dies/crimp-system-pliers-exchangeable-crimping-dies/9743200) ([version without case](https://www.knipex.com/products/crimping-pliers/crimp-system-pliers-for-exchangeable-crimping-dies/crimp-system-pliers-exchangeable-crimping-dies/9743200A)) or the [PreciForce® Crimping Pliers](https://www.knipex.com/products/crimping-pliers/knipex-preciforce-crimping-pliers/knipex-preciforcecrimping-pliers/975238) or the [Crimping Pliers for two-hand operation](https://www.knipex.com/products/crimping-pliers/crimping-pliers-for-two-hand-operation/crimping-pliersfor-two-hand-operation/975208)). Note that wire ferrules for wires smaller than 0.25 mm² can only be crimped by [Self-Adjusting Crimping Pliers for wire ferrules](https://www.knipex.com/search?keys=Self-Adjusting+Crimping+Pliers+for+wire+ferrules).

Also if your [VFD](https://en.wikipedia.org/wiki/Variable-frequency_drive) offers an internal [termination resistor](https://en.wikipedia.org/wiki/Electrical_termination) (my VFD does) then it’s good to turn it on, because expectedly your VFD is the last device on the [line](https://en.wikipedia.org/wiki/Serial_communication).

#### Further Reading

[CRC](https://en.wikipedia.org/wiki/Cyclic_redundancy_check)  
[Modbus RTU frame format](https://en.wikipedia.org/wiki/Modbus#Modbus_RTU_frame_format)

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