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//! Implements the `BatteryVoltage` feature (ID `0x1001`) that reports a
//! device's battery charge as a measured voltage plus a charging-flags byte.
//!
//! G-series wireless gaming devices (G915, G903 LS, G502 LIGHTSPEED) expose
//! `0x1001` and neither the legacy `0x1000` nor the unified `0x1004`, so
//! without this feature the inventory probe finds no battery source for them
//! at all. Unlike its siblings the feature reports no percentage — callers
//! estimate one from the voltage (see `openlogi-hid`'s mappings).
//!
//! Only `getBatteryInfo` (function `0`) is implemented. The device also
//! broadcasts event `0` when its voltage or charging state changes;
//! [`BatteryVoltageFeature::is_status_broadcast`] recognises it so a listener
//! can re-read the battery instead of waiting for a poll — the same scope
//! `BatteryStatus` (`0x1000`) keeps.
//!
//! The wire layout is not in a public Logitech spec: the voltage as a
//! big-endian millivolt `u16` followed by one flags byte was
//! reverse-engineered, and the decoding here follows Solaar
//! (`decipher_battery_voltage`) and libratbag's consensus on the flag bits.
//! The charge status values follow the Linux HID++ driver
//! (`hidpp20_battery_map_status_voltage`), which reads three status bits and
//! leaves values above `2` unknown.
use openlogi_hidpp_derive::Feature;
use crate::{feature::FeatureEndpoint, protocol::v20::Hidpp20Error};
/// Implements the `BatteryVoltage` / `0x1001` feature.
#[derive(Feature)]
#[creatable(id = 0x1001, version = 0)]
pub struct BatteryVoltageFeature {
/// The endpoint this feature talks to.
endpoint: FeatureEndpoint,
}
impl BatteryVoltageFeature {
/// Whether an unsolicited report on this feature's index is its
/// battery-voltage broadcast (event `0`; the Linux driver's
/// `EVENT_BATTERY_VOLTAGE_STATUS_BROADCAST`).
///
/// Deliberately independent of the payload, like
/// `BatteryStatusFeature::is_status_broadcast`: a listener that only needs
/// to know *that* the reading changed re-reads it with
/// [`Self::get_battery_info`].
#[must_use]
pub const fn is_status_broadcast(function_id: u8) -> bool {
function_id == 0
}
/// Reads the measured battery voltage and charging state (function `0`,
/// `getBatteryInfo`).
pub async fn get_battery_info(&self) -> Result<VoltageBatteryInfo, Hidpp20Error> {
let payload = self.endpoint.call(0, [0; 3]).await?.extend_payload();
Ok(VoltageBatteryInfo::from_wire(&payload))
}
}
/// A reading from the `0x1001` `getBatteryInfo` function.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[non_exhaustive]
pub struct VoltageBatteryInfo {
/// Measured battery voltage in millivolt — roughly `3500` (empty) to
/// `4200` (full) for the single-cell Li-Po batteries these devices carry.
pub voltage_mv: u16,
/// The charging state decoded from the flags byte.
pub status: VoltageChargingStatus,
/// The firmware's "charge level critical" marker (flags bit `5`).
pub critical: bool,
}
impl VoltageBatteryInfo {
/// Decodes a `getBatteryInfo` response payload: voltage as a big-endian
/// millivolt `u16` in bytes `0`–`1`, the charging flags in byte `2`.
#[must_use]
pub fn from_wire(payload: &[u8; 16]) -> Self {
let flags = payload[2];
Self {
voltage_mv: u16::from_be_bytes([payload[0], payload[1]]),
status: VoltageChargingStatus::from_flags(flags),
critical: flags & (1 << 5) != 0,
}
}
}
/// Charging state decoded from the `0x1001` flags byte.
///
/// Bit `7` set means external power is present; bits `0`–`2` then carry the
/// charge status (`0` charging, `1` charge complete, `2` charge fault, any
/// other value undefined) and bits `3` / `4` mark fast / slow charging.
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
#[cfg_attr(feature = "serde", derive(serde::Serialize))]
#[non_exhaustive]
pub enum VoltageChargingStatus {
/// Running on battery (bit `7` clear).
Discharging,
/// Charging at the standard rate.
Charging,
/// Charging at a raised current (bit `3`).
ChargingFast,
/// Charging at reduced current (bit `4`).
ChargingSlow,
/// On external power with charge complete (status bits `0b01`).
Full,
/// On external power but not charging — a charge fault (status bits
/// `0b10`).
NotCharging,
/// On external power with a status value the protocol leaves undefined
/// (bits `0`–`2` equal to `3` through `7`).
Unknown,
}
impl VoltageChargingStatus {
/// Decodes the flags byte. Total on purpose, so a battery reading never
/// vanishes over an unknown bit: an undefined status value decodes to
/// [`Self::Unknown`] and the voltage still reads. It does not borrow a
/// neighbouring bucket — that would show `0b011` as a full battery.
fn from_flags(flags: u8) -> Self {
if flags & (1 << 7) == 0 {
return Self::Discharging;
}
match flags & 0x07 {
0x00 => {
if flags & (1 << 3) != 0 {
Self::ChargingFast
} else if flags & (1 << 4) != 0 {
Self::ChargingSlow
} else {
Self::Charging
}
}
0x01 => Self::Full,
0x02 => Self::NotCharging,
_ => Self::Unknown,
}
}
}
#[cfg(test)]
mod tests {
use super::{VoltageBatteryInfo, VoltageChargingStatus};
/// Builds a 16-byte payload from the 3 meaningful bytes.
fn payload(voltage_mv: u16, flags: u8) -> [u8; 16] {
let mut payload = [0; 16];
payload[..2].copy_from_slice(&voltage_mv.to_be_bytes());
payload[2] = flags;
payload
}
#[test]
fn discharging_reading_decodes_voltage_and_status() {
let info = VoltageBatteryInfo::from_wire(&payload(3781, 0x00));
assert_eq!(info.voltage_mv, 3781);
assert_eq!(info.status, VoltageChargingStatus::Discharging);
assert!(!info.critical);
}
#[test]
fn external_power_flag_alone_means_standard_charging() {
let info = VoltageBatteryInfo::from_wire(&payload(4100, 0x80));
assert_eq!(info.status, VoltageChargingStatus::Charging);
}
#[test]
fn charge_status_bits_take_precedence_over_rate_bits() {
// Charge complete wins over a stale fast-charge bit.
let info = VoltageBatteryInfo::from_wire(&payload(4186, 0x80 | 0x08 | 0x01));
assert_eq!(info.status, VoltageChargingStatus::Full);
let info = VoltageBatteryInfo::from_wire(&payload(4000, 0x80 | 0x02));
assert_eq!(info.status, VoltageChargingStatus::NotCharging);
}
#[test]
fn rate_bits_split_fast_and_slow_charging() {
let fast = VoltageBatteryInfo::from_wire(&payload(3900, 0x80 | 0x08));
assert_eq!(fast.status, VoltageChargingStatus::ChargingFast);
let slow = VoltageBatteryInfo::from_wire(&payload(3900, 0x80 | 0x10));
assert_eq!(slow.status, VoltageChargingStatus::ChargingSlow);
}
#[test]
fn critical_bit_is_surfaced_independently_of_status() {
let info = VoltageBatteryInfo::from_wire(&payload(3520, 0x20));
assert_eq!(info.status, VoltageChargingStatus::Discharging);
assert!(info.critical);
}
#[test]
fn without_external_power_the_rate_bits_are_meaningless() {
// Bit 7 clear: whatever the low bits claim, the device runs on battery.
let info = VoltageBatteryInfo::from_wire(&payload(3700, 0x1b));
assert_eq!(info.status, VoltageChargingStatus::Discharging);
}
#[test]
fn on_external_power_only_status_values_0_to_2_are_defined() {
let cases = [
(0x80, VoltageChargingStatus::Charging),
(0x81, VoltageChargingStatus::Full),
(0x82, VoltageChargingStatus::NotCharging),
(0x83, VoltageChargingStatus::Unknown),
(0x84, VoltageChargingStatus::Unknown),
(0x85, VoltageChargingStatus::Unknown),
(0x86, VoltageChargingStatus::Unknown),
(0x87, VoltageChargingStatus::Unknown),
];
for (flags, expected) in cases {
let info = VoltageBatteryInfo::from_wire(&payload(4000, flags));
assert_eq!(info.status, expected, "flags {flags:#04x}");
assert_eq!(info.voltage_mv, 4000, "flags {flags:#04x}");
}
}
#[test]
fn rate_bits_do_not_turn_an_undefined_status_into_charging() {
// Status 4 with the fast-charge bit set is still an undefined status.
let info = VoltageBatteryInfo::from_wire(&payload(3900, 0x80 | 0x08 | 0x04));
assert_eq!(info.status, VoltageChargingStatus::Unknown);
}
}