HUB75-Differential_stepgen

HUB-75 Differential stepgen

Break-out board with 3 stepgen channels. As most stepper motor drivers are opto-isolated, the board does not provide any extra isolation.

NOTE
On the images the RJ45-connectors and the SO-16 packages are not displayed as their models are not available in KiCAD.

Features

• 2 HUB-75 input connectors
• 1 HUB-75 output connector for alarm
• 3 channel differential stepgen drivers using RJ-45 plugs with frequency up to 400 kHz
• status LEDs on RJ-45 plugs for Enable and Alarm
• selectable active HIGH or active LOW for Enable using dip-switches
• selectable active HIGH or active LOW for Alarm using dip-switches

Two differential stepgen BOBs can share HUB-75 output connector by setting the solder jumpers on the board for either stepgen 1-3 or stepgen 4-6.

Applications

• Driving stepper motor drivers with internal opto-couplers.

NOTE
To save on the number of outputs used, one can opt for a single ended version of the BOB.

Example wiring

Any standard UTP-cable can be used for as a 'donor' for connecting the BOB to the driver. One can either:

• cut the cable and use the wires in the screw-terminals of the driver.
• create a small break-out board with RJ45 connector which fits your driver. The pitch and the order of the pins makes this a custom solution for almost any driver. These break-out boards, when developed, will be shared here as well, listed by type of the driver. These will be designed to be DIY, as small PCB's tend to be expensive.

The pin-out of the cable is as folllows

RJ-45 pin	Color	Function
1	green/white	STEP-
2	green	STEP+
3	orange/white	GND
4	blue	ENA
5	blue/white	GND
6	orange	ALARM
7	brown/white	DIR-
8	brown	DIR+

Litex-CNC example configuration

Let's assume that the two output HUB-745 connectors on this board are connected to J1 and J2 of the FPGA and the input connector is J16. To configure the pins for output, you can use the configuration-block below as a starting point. Optionaly the pin names can also be set in the configuration, making the HAL clearer.

{
    ...,
    "stepgen": [
        {
            "step_pin": "j1:0",
            "dir_pin": "j1:1",
            "soft_stop": true
        },
        {
            "step_pin": "j1:2",
            "dir_pin": "j1:4",
            "soft_stop": true
        }
        {
            "step_pin": "j1:5",
            "dir_pin": "j1:6",
            "soft_stop": true
        },
        {
            "step_pin": "j2:0",
            "dir_pin": "j2:1",
            "soft_stop": true
        },
        {
            "step_pin": "j2:2",
            "dir_pin": "j2:4",
            "soft_stop": true
        }
        {
            "step_pin": "j2:5",
            "dir_pin": "j2:6",
            "soft_stop": true
        }
    ],
    "gpio_in": [
        {"pin": "j16:0", "name": "stepgen.0.alarm"},
        {"pin": "j16:1", "name": "stepgen.1.alarm"},
        {"pin": "j16:2", "name": "stepgen.2.alarm"},
        {"pin": "j16:4", "name": "stepgen.3.alarm"},
        {"pin": "j16:5", "name": "stepgen.4.alarm"},
        {"pin": "j16:6", "name": "stepgen.5.alarm"},
    ],
    "gpio_in": [
        {"pin": "j1:14", "name": "stepgen.enable"},
    ],
    ...
}

NOTE
The BOB uses pin 14 (OE) of the HUB-75 connector, which is a shared pin. This board therefore cannot be used in combination with other BOB's using the same pin when it's function is incompatible.

Bill of materials

The table below gives the bill of materials used for this BOB and an indication of its price. The list is available as public list for the following companies:

• Reichtelt. This is non-affiliate link, I do not earn any money when you order this list from this specific vendor, nor the vendor endorses this project. Reichtelt is a supplyer for Western Europe.

When you order with Mouser or antohter supplier, please share a list here.

Part. number	Package	Description	Datasheet	Amount	Price*
74HC86	SO-16	Quad XOR-gates		2	€ 0.16
SMD 1/4W270	SMD 1206	Resistor, 270 Ohm		6	€ 0.03
SMD 1/4W 10K	SMD 1206	Resistor, 10 kOhm		12	€ 0.03
X7R-G1206 100N	SMD 1206	Capacittor 100 nF		12	€ 0.22
DIP 3P	DIP-6	DIP-switch, 3P		2	€ 0.33
DG250 3,5-2	-	Screw/spring terminal 2.5 mm pitch		1	€ 0.22
BOX 2X8	-	Box header 2x8, 2.54 mm pitch		3	€ 0.16
CAT5	-	RJ-45 Bus with LED**		3	€ 1.07

NOTES:

1. The price is based on availability in the Netherlands with a single shop for all parts. Parts might be sourced cheaper depending on your location, available sources and the time you want to wait before receiving the components.
2. When using a different source for the connector, please verify the footprint, as there are many variants.

Known issues

This board does not have any known issues yet.

If you find any issue, please file a bug using GitHub.

Version history

1.1

• Changed HUB75 connectors from pin headers to IDC connectors (shrouded). Moved several components to make space for the larger footprint
• Wired alarm 1-3 to pin 1-3 of J3 (was pin 3-5-7, which was not logical for config). Wired alarm 4-6 to pin 5-7 of J3 (NOTE: pin 4 is GND). Version 1.0 boards cannot be connected to version 1.1 boards due to this change.
• Added labels to clarify the function of the DIP-switches and solder jumpers.

1.0

• Initial version for proto-type.