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BCB Bluetooth Protocol


This page describes the Bluetooth communication protocol for the control and diagnostics of the iCub battery backpack system. The iCub backpack communicates via the BCB electronic board, which embeds a Bluetooth module. To pair with it, no special passwords or codes are needed; the electronic board is always visible from any other device, it is called RNBT-F29x, and must be considered as a SLAVE.

After turned on, when pairing has not yet taken place: - the blue LED DL5 will blink - the green LED DL4 will be on and fixed

both LEDs are next to the Bluetooth module as shown in the following figure:

After pairing, the blue LED turns on steadily and the green LED turns off. If there is data transfer in transmission or reception, the orange LED DL6 will flash.

Communication characteristics

Baud rate 115200, 8 data bits, parity none, stop-bit one.

Types of data in transmission and reception

The data transferred through Bluetooth concern the parameters of the iCub battery, system status feedback, sending of commands.

List of commands

Write data

The following table shows the bytes that can be sent and the corresponding function.

Command Description
0x00 Disable data transfer
0x01 Enable data transfer
0x10 PC104 power on
0x11 PC104 shutdown
0x20 Motors power on
0x21 Motors shutdown
0xFF Firmware version of the BCB board

If data transfer is enabled, the blue led on the card will blink.

Note: in the event of a fault on the PC104 and/or motors (overcurrent anomaly), the corresponding power supply must be reset using the buttons on the backpack by pressing the flashing red LED button for a few seconds. In any case, investigate or report the problem.

Read data

If data transmission is enabled, the BCB board continuously sends the battery status information (voltage, current, charge), the status of the DC/DC converters (ON, OFF, fault), and the status of the Hot Swap Manager (power good, fault). It also signals a possible restart following a fault. The string sent is made up of 10 bytes:

RX[0] RX[1] RX[2] RX[3] RX[4] RX[5] RX[6] RX[7] RX[8] RX[9]
0x00 Battery Voltage (MSB) Battery Voltage (LSB) Battery current (MSB) Battery current (LSB) Battery Charge (MSB) Battery Charge (LSB) Backpack Status \r \n

The values of the parameters are obtained as follows:

  • \(\text{Battery voltage} = RX[1] \cdot 256 + RX[2] \; \text{expressed in mV}\)
  • \(\text{Battery current} = RX[3] \cdot 256 + RX[4] \; \text{expressed in mA}\)
  • \(\text{Battery charge} = RX[5] \cdot 256 + RX[6] \; \text{expressed in %}\)

The status byte RX[7] is divided as follows:

RX[7] (bit 7..0) Description
Bit 7 1-> PC104 on, 0-> PC104 off
Bit 6 1-> PC104 fault , 0-> PC104 ok
Bit 5 1-> Motors on, 0-> Motors off
Bit 4 1-> Motors fault , 0-> Motors ok
Bit 3 1-> HSM on, 0-> HSM off
Bit 2 1-> HSM running, 0-> HSM not ready yet
Bit 1 1-> HSM fault, 0-> HSM ok
Bit 0 1-> restarting after a fault, 0-> normal operation