write

Writes a message to a GATT characteristic. Devices that support commands (Motherboard, Progressor, Force Board) expose a commands object-a standardized interface mapping semantic names (e.g. GET_BATTERY_VOLTAGE) to device-specific payloads. Pass device.commands.COMMAND_NAME as the message. An optional callback receives the characteristic's response (e.g. battery voltage, serial number).

Signature

write(
  serviceId: string,
  characteristicId: string,
  message: string | Uint8Array | undefined,
  duration?: number,
  callback?: (data: string) => void,
): Promise<void>

Parameters

Parameter	Type	Default	Description
serviceId	string	-	Service identifier.
characteristicId	string	-	Characteristic identifier (e.g. "tx").
message	string | Uint8Array | undefined	-	Command or payload to write.
duration	number	0	Milliseconds to wait before resolving.
callback	(data: string) => void	-	Optional callback for characteristic response.

Returns

Promise<void> - Resolves when the write completes.

Example

import { Progressor } from "@hangtime/grip-connect"

const device = new Progressor()

await device.connect(
  async () => {
    await device.write("progressor", "tx", device.commands.GET_BATTERY_VOLTAGE, 250, (data) =>
      console.log("Battery voltage:", data),
    )
  },
  (err) => console.error(err),
)

Types

Type	Description
WriteCallback	(data: string) => void - receives the characteristic's response.

Response

The optional callback receives a string - the characteristic's response (e.g. battery voltage, serial number).

Commands

Devices that support commands (Motherboard, Progressor, Force Board) map semantic names to protocol-specific payloads. Use device.commands.COMMAND_NAME as the message-each device defines its own values. Common commands:

Command	Description	Devices
START_WEIGHT_MEAS	Start force streaming	Motherboard, Progressor, Force Board
STOP_WEIGHT_MEAS	Stop streaming	Motherboard, Progressor, Force Board
SLEEP	Put device to sleep	Motherboard, Progressor
GET_SERIAL	Get serial number	Motherboard
GET_BATTERY_VOLTAGE	Get battery voltage	Progressor
GET_FIRMWARE_VERSION	Get firmware version	Progressor
TARE_SCALE	Tare (zero) the scale	Progressor, Force Board
START_QUICK_MEAS	Quick measure mode	Force Board

See Devices for which commands each device supports.