Lego EV3 - Get output device type, opOUTPUT_GET_TYPE

Question

I would like to know what kind of motor (XL, L) is connected to EV3 output port (A|B|C|D). I need to use direct command:

Instruction        opOutput_Get_Type (LAYER, NO, *TYPE)
Opcode             0xA0
Arguments          (Data8) LAYER – Specify chain layer number [0 - 3]
                   (Data8) NO – Port number [0 - 3]
                   (Data8) *TYPE

so request should looks like:

unsigned const char opOutput_Get_Type[] {
    0x09, 0x00, // bytes in message
    0x00, 0x00, // message counter
    0x00,       // DIRECT_COMMAND_REPLY
    0x01, 0x00, // 1 value will be returned
    0xA0,       // opOutput_Get_Type
    LC0(0),     // LAYER 0, first brick in chain
    LC0(0),     // port A
    GV0(0)      // returned value
};

When I send it to brick a get response:

04000000 0400
          ^-
          DIRECT_REPLY_ERROR

which stands that error occurred. Motor is connected to port A. What am I doing wrong?

Answer 1

Checking the source code, it appears that the opOutput_Get_Type command is not implemented. In both links, it is mentioned in the comments, but there is nothing in the actual code.

Unfortunately, I am not finding a different way to get this information.

Answer 2

The one who wants to know device type should use direct command:

Instruction        opInput_Device (CMD, ...)
Opcode             0x99
CMD                GET_TYPEMODE = 0x05
Arguments
                   (Data8) LAYER – Specify chain layer number [0 - 3]
                   (Data8) NO – Port number [0 - 3]
Returns
                   (Data8) TYPE
                   (Data8) MODE - Device mode [0-7]

In order to discover all ports we should send

unsigned const char opOutput_Get_Type[] {
    0x35, 0x00,                                 //Message size = 53 bytes (0x35 hex)
    0x00, 0x00,                                 //Message Counter
    0x00,                                       //DIRECT_COMMAND_REPLY
    0x10, 0x00,                                 //16 values will be returned... 8 pairs (type, mode)
    0x99, 0x05, 0x00, 0x00, GV0(0), GV0(1),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_A, TYPE, MODE
    0x99, 0x05, 0x00, 0x01, GV0(2), GV0(3),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_B, TYPE, MODE
    0x99, 0x05, 0x00, 0x02, GV0(4), GV0(5),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_C, TYPE, MODE
    0x99, 0x05, 0x00, 0x03, GV0(6), GV0(7),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_D, TYPE, MODE
    0x99, 0x05, 0x00, 0x10, GV0(8), GV0(9),     //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_1, TYPE, MODE
    0x99, 0x05, 0x00, 0x11, GV0(10), GV0(11),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_2, TYPE, MODE
    0x99, 0x05, 0x00, 0x12, GV0(12), GV0(13),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_3, TYPE, MODE
    0x99, 0x05, 0x00, 0x13, GV0(14), GV0(15),   //opInput_Device, GET_TYPEMODE, LAYER_0, PORT_4, TYPE, MODE
};

In return we'll get response i.e.:

13 00 00 00 02 7e 00 7e 00 7e 00 7e 00 08 00 07 00 07 00 7e 00

which stands (based on http://ev3.fantastic.computer/doxygen/types.html)

13 00   //message size = 19 bytes
00 00   //message counter
02      //success
7e 00   //nothing on port A
7e 00   //nothing on port B
7e 00   //nothing on port C
7e 00   //nothing on port D
08 00   //M-MOTOR-DEG on port 1
07 00   //L-MOTOR-DEG on port 2
07 01   //L-MOTOR-ROT on port 3
7e 00   //nothing on port 4