sys_status.cpp: Do not use battery1 voltage for all batteries.

[amilcarlucas]

Do not use battery1 voltage as voltage for all other batteries (bugfix).
Support both cell and total voltages above 65V
Support up-to 14S batteries
If available, add cell voltage information to the battery diagnostic

Tested on a drone with 3 batteries, and multiple cells

[vooon]

Please explain unclear operation with cell_voltage vector.
Also processing voltages and voltages_ext might be done in lambda, so you could remove duplicate.

[vooon]

That's unclear to me. Why do you need nr_cells? Why not to use cell_voltage.size()?
And why do you need to erase()? reserve() do not change size(), only capacity().

[amilcarlucas]

Why do you need nr_cells? Why not to use cell_voltage.size()?

because if for some reason a cell has more than 65,534V it get coalesced with the next one. Hence the bookkeeping with the extra variable.

And why do you need to erase()?

Using erase allows up to neatly only present the actual number of cells in the ROS message.

reserve do not change size(), only capacity().

Yes, I an aware of that. This method gets a neat result with very low complexity. Erase will not realloc, nor move data around.

processing voltages and voltages_ext might be done in lambda, so you could remove duplicate.

The handling in voltages and voltages_ext is different. The duplication is required. :(

[amilcarlucas]

Sorry, you are 100% correct about using .size() and removing nr_cells

I changed it now, and corrected other small innacuracy

[vooon]

nr_cell always will be equal to size() because it's increase done after push_back().
Lambda could look like that:

int32_t volt_acc = 0;
float total_volt = 0.0f;
auto copy_cell = [&](uint16_t v, bool is_ext) {
  if (v == UINT16_MAX || (is_ext && v == 0))
    return;
    
  if (v == UINT16_MAX-1) {
    volt_acc += v;
    return;
  }
  
  float cv = (volt_acc + v) * 0.001f;
  volt_acc = 0; // clear accumulator after use
  batt_msg->cell_voltage.push_back(cv);
  total_volt += cv;
}

for (auto v : bs.voltages) copy_cell(v, false);
for (auto v : bs.voltages_ext) copy_cell(v, true);

[vooon]

And about ROS message: you don't have to worry about erasing capacity(), only size() matters.

[vooon]

// i'm curious, that chemistry type has so huge cell voltage?

[amilcarlucas]

yes, you are correct the erase() is not needed at all. Removed it, sorry.

[amilcarlucas]

I'm not sure about chemistry but if you have a > 16S battery, you will need that mechanism to correctly get the battery voltage. According to the mavlink standard:
https://mavlink.io/en/messages/common.html#BATTERY_STATUS

[vooon]

Ah, yes, so that a hack to send above 65 total volts. I changed lambda to be able to handle more than one (2**16-2) "cells".
Please note that your code has error in else {acc=0} block because you're clearing accumulator before use.

[amilcarlucas]

rebased

[amilcarlucas]

Thanks for spoting that nasty bug. fixed and squashed all commits.

[vooon]

LGTM, Thanks!