# Gripper

The move command, its answer, and the gripper calibration. [How the gripper works](https://docs.source-robotics.com/SSG48-gripper-docs/2/06-operation/how-it-works/)
explains what the gripper does with them.

### Send_gripper_data_pack

<div class="cmd-facts" markdown><span class="fact">ID 61</span><span class="fact">host → driver</span><span class="fact">0 or 5 bytes</span><span class="fact">Python: `Send_gripper_data_pack()`</span></div>

The gripper command, for a driver set up as a gripper (`#Gripper 1`, saved). Position, speed and the current limit of the move, plus the activate, action and E-stop bits. A move is carried out only while the gripper is calibrated, activated and the action bit is 1. An empty frame (0 bytes) only asks for the state. The answer is sent before the driver acts on the frame, so it carries the state from before it. While the gripper calibration runs, send only the empty frame: a full one ends the calibration.

**5 bytes**

| Byte | Bit | Field | Type | Meaning |
|---|---|---|---|---|
| 0 |  | Position | unsigned 8-bit | 0 fully open, 255 fully closed |
| 1 |  | Speed | unsigned 8-bit | 0 slowest, 255 fastest |
| 2-3 |  | Current | signed 16-bit | current limit of the move in mA, the grip force; not clamped by the firmware, see Force and speed for the safe range |
| 4 | 7 | Activate | bit | 1 activate the gripper, 0 deactivate |
| 4 | 6 | Action | bit | 1 go to the position, 0 idle |
| 4 | 5 | E-stop | bit | 1 raises the gripper E-stop error, again at every cycle while the last command's bit is 1 |
| 4 | 4 | Release direction | bit | read by the firmware but not used |

The driver answers with **Respond_Gripper_data_pack**.

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### Respond_Gripper_data_pack

<div class="cmd-facts" markdown><span class="fact">ID 60</span><span class="fact">driver → host</span><span class="fact">4 bytes</span></div>

The driver's answer to Send_gripper_data_pack: position, measured current, and the state bits. Python attributes `gripper_position`, `gripper_current`, `gripper_activated`, `gripper_action_status`, `gripper_object_detection`, `gripper_temperature_error`, `gripper_timeout_error`, `gripper_estop_error`, `gripper_calibrated`.

**The frame** (4 bytes)

| Byte | Bit | Field | Type | Meaning |
|---|---|---|---|---|
| 0 |  | gripper_position | unsigned 8-bit | 0 fully open, 255 fully closed |
| 1-2 |  | gripper_current | signed 16-bit | measured current in mA |
| 3 | 7 | gripper_activated | bit | 1 activated |
| 3 | 6 | gripper_action_status | bit | the action bit of the last command, as received; stays 1 while holding, not changed by the calibration |
| 3 | 5-4 | gripper_object_detection | 2 bits | bit 5 is the low bit, bit 4 the high bit: 0 moving, 1 object detected while closing, 2 object detected while opening, 3 at the position |
| 3 | 3 | gripper_temperature_error | bit |  |
| 3 | 2 | gripper_timeout_error | bit |  |
| 3 | 1 | gripper_estop_error | bit |  |
| 3 | 0 | gripper_calibrated | bit | 1 calibrated |

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### Send_gripper_calibrate

<div class="cmd-facts" markdown><span class="fact">ID 62</span><span class="fact">host → driver</span><span class="fact">0 bytes</span><span class="fact">Python: `Send_gripper_calibrate()`</span></div>

Starts the gripper calibration (the jaws find their end stops). Needed after every power-up. It has no answer: poll with empty Send_gripper_data_pack frames until the calibrated bit is 1, and send nothing else meanwhile, since a full gripper command or Send_Clear_Error ends the calibration. With an error active the request is dropped: clear first.

The driver does not answer this command.

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