This page documents how the Ring Fit Adventure game uses hidbus for using the Ring-Con ExternalDevice, which attaches to Joy-Cons.

The BusType used with GetBusHandle is value 0 or 1.

The ExternalDeviceId is 0x20. After EnableExternalDevice is used successfully during initialization, EnableJoyPollingReceiveMode(flag=true) is used with 4-byte command 0x020101. For cleanup, DisableJoyPollingReceiveMode is used then on success EnableExternalDevice(flag=false) is used.

Commands (input data for EnableJoyPollingReceiveMode / SendAndReceive) start with the u32 cmd, there's generally no data after that. Data in the replies are at least 0x4-bytes, with fields being 4-byte aligned. Reply+0 is the u8 status. When the output size doesn't match the expected size, or status is non-zero, error 0xEDA is returned. When status is non-zero, a func is called with the status value which updates global state.

The status field is not listed below since all replies have it.

CRC

Some commands/replies use CRC(s) for validating the previous N-bytes prior to the CRC. When the CRC is invalid, the app sets an output flag indicating invalid CRC and skips writing output-data to the output-param.

This CRC doesn't use Xor(In/Out)/Reflect(In/Out). The polynomial is 0x8D.

Commands

Input cmd u32	Input cmd size	Reply size
0x020000	0x4	0x8
0x020101	0x4	0x8

0x20000

The two u8s at reply+0x4 are copied to an output struct.

0x020101

This is used with EnableJoyPollingReceiveMode/GetJoyPollingReceivedData. Reply+0x4 is an u16 which is copied to an output struct, the timestamp is also copied.