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I don't think there is much advantage to returning the rotary encoder
data to LinuxCNC.  I think for the uses of the linear encoder position mode
is OK, basically the linear encoder would be of most use compensating for
ball screw errors and thermal expansion which can be handled by LinuxCNCs
relatively low bandwidth control.

The RS-485 adapter should work, wiring would be:

PktURDataPin  <= RO   
PktUTDataPin   => DI
PktUTNDrvEnPin => DE
GND => RE

Note the N in PktUTNDrvEnPin

(the firmware must be built with this pin in the pinout file to have the
proper drive enable polarity)

Did you look at the relayboard.mod example?
Its probably closer, not for addresses but for bit I/O:
(look an the input definition)


/* Modbus definition file for a 4-channel relay board found on eBay */

/*
The format of the channel descriptors is:

{TYPE, FUNC, ADDR, COUNT, pin_name}

TYPE is one of HAL_BIT, HAL_FLOAT, HAL_S32, HAL_U32
FUNC = 1, 2, 3, 4, 5, 6, 15, 16 - Modbus commands
COUNT = number of coils/registers to read
*/

#define MAX_MSG_LEN 16   // may be increased if necessary to max 251

static const hm2_modbus_chan_descriptor_t channels[] = {
/*  {TYPE,    FUNC, ADDR,   COUNT, pin_name} */
    {HAL_BIT, 1,  0x0000, 8,     "state"},
    {HAL_BIT, 2,  0x0000, 8,     "input"},
    {HAL_BIT, 5,  0x0000, 1,     "relay-0"},
    {HAL_BIT, 5,  0x0001, 1,     "relay-1"},
    {HAL_BIT, 5,  0x0002, 1,     "relay-2"},
    {HAL_BIT, 5,  0x0003, 1,     "relay-3"},
};


/* Optionally #define DEBUG to aid with troubleshooting.
   Use 3 to see a lot of information about the modbus
   internal workings. 1 is default (errors only)                    */

 

Hi.
I would like to come back to you about the best way to have a closed loop with a linear scale and a servodrive-motor combination (which has a closed loop already)

Please take a look at attached picture.
The motor has an encoder which is connected to the drive.
The Mesa-board sees the exact position of the table, and should keep giving commands to the drive, untill position is reached. (I expect)

The loop between motor-encoder and drive is the fastest, and not influenced by any speed of the Mesa.

What is your opinion of the considerations I have:
1. Is it smart to use the drive-outputs of the encoder to the Mesa-board? (And for what purpose)
2. Should I controll the drive in POSITION-mode or SPEED-mode?
 
Thanks, and with kind regards.

That's even better!

Added video to Lenovo T470
forum.linuxcnc.org/18-computer/54369-use...hernet-boards#313954

Hello dschultz,
could you share your working configuration?
I have the same servo but are not able to switch it to OP mode.
Thanks!