Specifications (from the EE Team)

Overall Hardware Architecture (taken from https://uwarg-docs.atlassian.net/wiki/x/AoCsmQ )

Background

The drone uses a battery pack containing 12 cells, where 2 groups of 6 cells are each connected in series (hence 6S).

Each group of 6 cells is connected to a battery monitoring circuit.

This circuit measures:

The voltage of each cell
The current delivered by the group

And it sends:

We are not exactly sure of everything yet.

Battery-related information relating to the voltages and currents
The voltage and current information are sent as 2 analog signals, which our microcontroller converts to digital ones via an Analog-to-Digital Converter (ADC).
Some other information is sent via the I²C protocol

Description

MCU (STM32xX) in the top right is the microcontroller that we are writing the code to
Its job is to translate the messages it receives from the BQ76925 6s LiPo Battery Monitor boards and send the corresponding messages to the flight controller (FC) using the CAN protocol

Why are we making this?

The FC needs this information to make other decisions, e.g. if a part is consuming too much power, or when to land

Specific Hardware Information (from https://uwarg-docs.atlassian.net/wiki/x/HYBXq)

The ports we are interested in:

PA9: SCL_1
PA10: SDA_1
PA7: SCL_2
PB4: SDA_4
PA12: CAN_TX
PA11: CAN_RX

Speculated ports:

PA3: Receives a digital signal representing whether an overcurrent occurred
PA5: Receives an analogue signal representing the cell voltages for cells 1-6
PB0: Receives an analogue signal representing the cell currents for cells 1-6
PB1: Receives an analogue signal representing the cell voltages for cells 7-12
PA2: Receives an analogue signal representing the cell currents for cells 7-12

\uD83E\uDD14 Current Roadblocks

Libcanard has a high learning curve. Neither the DroneCAN website nor the Libcanard repo has beginner-friendly tutorials. YouTube videos also won’t help directly

Tasks Break Down:

✅ Action Items

etc.

\uD83D\uDEA9 Milestones

Understand project specifications
Understand the I²C protocol
Understand the CAN protocol
Understand DroneCAN
etc.

Open Questions

Are our speculated ports correct?
What is transmitted over I²C?
What is the voltage range for the signals our MCU receives for the voltage and current info from the battery monitoring circuits?
How should the MCU beacon itself to the FC (i.e. so that the FC is aware that the MCU on the power module is there)?
What should be sent over CAN?

\uD83D\uDD17 Reference materials

Relevant protocols

I²C: I2C - Inter-Integrated Circuit
CAN:
- A general description of CAN: https://uwarg-docs.atlassian.net/wiki/x/BgDPlw
- DroneCAN: a protocol built on top of CAN to communicate information between drone parts and the FC: https://dronecan.github.io/
  - Libcanard: an implementation of DroneCAN for low-end microcontrollers. An example code on how to use it: https://github.com/dronecan/libcanard/blob/master/examples/SimpleNode/simple_node.c
- A helpful presentation on CAN: https://docs.google.com/presentation/d/12i6TiUuXQw5mO2u3pq8DMXTD1bCRe8rJtzVZRk6pDz0/edit?usp=sharing
- A helpful document on CAN applications: https://uwarg-docs.atlassian.net/wiki/x/AwA8q

6s Power Module