SPI ACCESSORY · A4988 SOCKET

SPI Adapter for A4988 Socket

This small adapter lets a compatible PiBot StepStick/A4988 socket route SPI to an external PiBot SilentStep TMC5160 V5 driver in SPI Independent mode.

V5.88 UltraV4.96 ProOne CS per driverAdapter only

Purpose & compatibility Install & wire FluidNC YAML First-power check Troubleshooting Guides & downloads

Power off before fitting. This is a signal adapter, not a stepper driver. Do not connect a motor or motor-power supply to this module. The TMC5160 V5 remains the motor driver.

Section 1Purpose and compatibility

What it routes

SPI Independent mode gives every external TMC5160 its own chip-select line. This adapter occupies a compatible A4988/StepStick socket and routes that socket's SPI signals and per-axis CS to the external driver connection.

What it does not do

It is not a stepper driver, a motor-output board or a power converter. It does not add a documented SPI-driver interface to V5.77 Carrier or V4.7B.

Use it for

V5.88 Ultra — SPI Independent mode

Use the adapter in the selected onboard StepStick socket.

V4.96 Pro — external SPI Independent mode

Follow the V4.96 slot-jumper settings shown in the driver guide.

You do not need it for

Normal / Standalone step-dir mode

Current and microstepping come from the driver's own DIP switch.

SPI Daisy Chain mode

The chain uses a single chip-select line, so no socket breakout is required.

V5.77 Carrier or V4.7B

Those configurations documented on this Wiki do not use this adapter.

Section 2How do I use it?

V5.88 Ultra

1

Turn off USB and main power.

2

Set the controller driver VDD and the TMC5160 V5 logic selection to 3.3 V.

3

Insert the adapter in the correct StepStick socket, matching the key/orientation. Connect the external TMC5160 V5 as shown below.

4

Use a separate CS line for each driver and the matching Independent-mode YAML.

V4.96 Pro

1

Turn off USB and main power.

2

Set the SPI logic side to 3.3 V.

3

Set the V4.96 slot jumpers for the external driver position, then insert the adapter in the matching socket.

4

Use one CS line per external TMC5160. Do not reuse the Daisy Chain wiring or YAML.

V5.88 Ultra with external TMC5160 V5 in SPI Independent mode

V5.88 Ultra · SPI Independent mode
The yellow adapter in the photograph is the same accessory shown as the socket-to-SPI module in this connection method.

V4.96 Pro with external TMC5160 V5 in SPI Independent mode

V4.96 Pro · SPI Independent mode
Use the V4.96 slot jumpers exactly as shown in the full driver connection guide.

Independent mode means one chip-select per driver. In the TMC5160 V5 configuration files this shows up as an individual cs_pin on every axis together with spi_index: -1, instead of the single cs_pin and counting spi_index used by a daisy chain.

Section 3FluidNC YAML for Independent mode

Independent mode gives every TMC5160 its own cs_pin. Each driver uses spi_index: -1; do not copy the numbered spi_index used by a daisy chain.

tmc_5160:
  cs_pin: I2SO.3       # example: first connector only
  spi_index: -1        # independent SPI mode
  r_sense_ohms: 0.1
  run_amps: 1.2
  hold_amps: 0.5
  microsteps: 16
  step_pin: I2SO.2
  direction_pin: I2SO.1
  disable_pin: I2SO.0

This is a pattern, not a machine-ready file. Confirm the CS and motion pins for the selected controller position, then set motor current, travel, homing, limits and steps/mm for the real machine. The complete four-axis examples are linked in section 6.

Section 4First-power and communication check

Before applying power

1

Check the adapter orientation, socket key and every jumper with USB and main power removed.

2

Confirm 3.3 V logic on the controller, adapter route and TMC5160 V5.

3

Verify MOSI, SCK, MISO, unique CS and common GND against the correct controller diagram.

Communication test

1

Power the controller and driver only after the wiring check is complete.

2

Open the FluidNC console and send $MI.

3

Confirm every configured TMC5160 is detected before attempting motion. Power down before changing any connection.

Pass

$MI lists every expected driver with sensible status values. Power down, connect the secured machine, then perform a slow test jog.

Fail — stop here

If a driver is missing or reports an abnormal status, do not jog. Remove power and check the items in section 5.

Section 5Troubleshooting

Driver not detected

Check the adapter is in the intended socket and is not rotated.
Check 3.3 V logic selection on both controller and TMC5160 V5.
Confirm every driver has a unique CS and spi_index: -1.
Check MOSI, SCK, MISO, CS and GND continuity with power removed.
Confirm the external TMC5160 has its required 24 V supply.

Detected, but motion is wrong

Stop motion and check STEP, DIR and EN mapping against the controller table.
Check motor coil order at the TMC5160 driver, not at the adapter.
Confirm current and microsteps are appropriate for the motor.
Do not change wiring or jumpers while powered.

Never troubleshoot by moving a powered adapter or jumper. Remove USB and main power first. If a module becomes hot, smells unusual or shows visible damage, disconnect power immediately and do not reuse it until the wiring has been checked.

Section 6Guides and downloads

Use the main TMC5160 V5 guide for the complete wiring, CS mapping, logic-voltage jumpers and controller-specific diagrams. Use the ready-made examples as a checked starting point, then adapt machine parameters deliberately.

SilentStep TMC5160 V5 guide Ready-made 4-axis YAML files V4.96 driver guide TMC5160A datasheet

Module colour may vary between production batches. Identify it by the A4988/StepStick socket format and SPI-adapter function, not by PCB colour alone. If the PCB revision or jumper silk changes, follow the marking on the physical module and the current controller guide.