...

This circuit measures:

The voltage of each cell
The current delivered by the group
- This is done by forcing the battery to deliver current through a resistor with a tiny resistance. This resistor, called a shunt/shunt resistor, follows Ohm’s law: V=IR
- This implies that I=V/R, which means that the current passing through a shunt is equal to its voltage (which can be measured easily), divided by its resistance (which is a known constant).

And it sends:

Note
We are not exactly sure of everything yet.

...

Info

The ports we are interested in:

Speculated ports:

, Receive line for CAN
PA3: Receives a digital signal representing whether an overcurrent occurredPA5: Receives an analogue signal OVERCURRENT, receives 5.5 V when an overcurrent occurs, and 0 V otherwise

Speculated ports:

PA5: VCOUT1_FILT, receives 1.47-1.53 V (REF_SEL=0) / 2.94-3.06 V (REF_SEL=1), representing the cell voltages for cells 1-6
PB0: Receives an analogue signal ADC1_FILT, receives 0.25-1.25 V (REF_SEL=0) / 0.5-2.5 V (REF_SEL=1), representing the cell currents current for cells 1-6PB1: Receives an analogue signal , as measured by a 1-milliohm shunt
PB1: VCOUT2_FILT, receives 1.47-1.53 V (REF_SEL=0) / 2.94-3.06 V (REF_SEL=1), representing the cell voltages for cells 7-12
PA2: Receives an analogue signal ADC2_FILT, receives 0.25-1.25 V (REF_SEL=0) / 0.5-2.5 V (REF_SEL=1), representing the cell currents current for cells 7-12, as measured by a 1-milliohm shunt

...

\uD83E\uDD14 Current Roadblocks

...

Open Questions

What is REF_SEL set to for the battery monitoring boards?
Are our speculated ports correct?
What is transmitted over Why are we reading the battery and voltage information via both I²C ?What is the voltage range for the signals our MCU receives for the voltage and current info from the battery monitoring circuitsand analogue pins?
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?

...

I²C: I2C - Inter-Integrated Circuit
- I²C is all about registers (i.e. memory that can be accessed by an address)
- Each I²C peripheral has its own register map (i.e. what the registers are used for, such as storing the voltage of a cell)
- To read data from a peripheral, you send an address to it, and it will respond with data
- To write data to a peripheral, you tell it which address to write to, and what data to write
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

...