atm90e32-async

Async no_std driver for the Microchip / Atmel ATM90E32 3-phase SPI power metering IC.

Built on top of embedded-hal-async, with no hard dependency on any specific async runtime — works with Embassy, RTIC2, or any executor that provides SpiDevice and DelayNs.

Architecture

The crate is split into a sans-I/O core and an async transport layer:

proto — pure functions: byte-frame building, response parsing, raw → engineering-unit conversions, and the post-reset init sequence materialised as data ([InitStep; 22]). 100% host-testable.
driver — the Atm90e32<SPI, D> struct: wraps SPI reads/writes, drives the init sequence, issues delays through a generic DelayNs.

The practical effect is that the tricky parts — wire format, 32-bit power-register assembly, signed power-factor decoding, line-frequency dependent MMode0 bit flip — are covered by 18 host unit tests and don't need a mock SPI bus.

Features

What the current version does:

Chip presence probe via SysStatus0
Full init sequence (soft reset, unlock, enable, calibration gains, startup thresholds, freq thresholds, PGA, MMode0/1, lock) driven by a single Config struct
Bulk 3-phase readout: RMS voltage, RMS current, active power, reactive power, power factor, mains frequency, phase angle
Per-phase reads for each of the above
Phase status decoding: per-phase overcurrent, overvoltage, voltage sag, phase loss, frequency warnings — from EMMState0/EMMState1
Chip temperature readout
Raw register read/write escape hatch (read_register / write_register)
Typed errors: Error::Spi(E), Error::NotPresent, Error::InitFailed(InitStage) with a per-step breakdown
Optional defmt::Format derives behind the defmt feature
No heap, no global state, no hard runtime dependency

What is not yet implemented (PRs welcome):

Energy accumulation (EPosA/EPosT/…)
Apparent power (S) registers
Harmonic analysis registers
Zero-crossing interrupts
Calibration assist helpers (auto-gain)
ATM90E36 family support (planned — the code layout anticipates it)
ATM90E26 (8-bit addressing, out of scope)

Quick start

use atm90e32_async::{Atm90e32, Config, LineFreq, PgaGain};

async fn run<SPI, D>(spi: SPI, delay: D) -> Result<(), atm90e32_async::Error<SPI::Error>>
where
    SPI: embedded_hal_async::spi::SpiDevice,
    D:   embedded_hal_async::delay::DelayNs,
{
    let mut meter = Atm90e32::new(spi, delay);
    meter.probe().await?;

    let cfg = Config::default()
        .with_voltage_gain([39470, 39470, 39470])
        .with_current_gain([65327, 65327, 65327])
        .with_line_freq(LineFreq::Hz50)
        .with_pga_gain(PgaGain::X2);
    meter.init(&cfg).await?;

    let r = meter.read_all_phases().await?;
    // Raw values — no f32 conversion until you need it:
    // r.voltage[0] is hundredths of a volt (u16)
    // r.power[0] is signed combined register word (i32)

    // Convert on demand:
    use atm90e32_async::proto;
    let volts = proto::voltage_raw_to_volts(r.voltage[0]);

    let status = meter.read_status().await?;
    // status.overcurrent, status.overvoltage, status.voltage_sag, status.phase_loss
    // status.is_ok()

    let temp_raw = meter.read_chip_temperature().await?;
    let temp_c = proto::temperature_raw_to_celsius(temp_raw);
    Ok(())
}

For a real integration on an ESP32 + Embassy + esp-hal, see the sketch in examples/basic.rs.

Hardware requirements

SPI mode 3 (CPOL=1, CPHA=1), MSB-first
SPI clock ≤ 16 MHz (datasheet limit)
One GPIO for chip select — exposed through the caller's SpiDevice implementation (e.g. embedded-hal-bus::spi::ExclusiveDevice)

The driver itself is transport-agnostic and works with any embedded-hal-async::spi::SpiDevice implementation.

Datasheet

ATM90E32AS datasheet (Microchip)

MSRV

Minimum supported Rust version is 1.75, required by embedded-hal-async 1.0 (async-fn-in-traits). MSRV is part of the semver contract and will only be bumped with a minor version release.

License

Dual-licensed under either of:

Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
GNU General Public License, Version 2.0 or later (LICENSE-GPL or https://www.gnu.org/licenses/old-licenses/gpl-2.0.html)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in this project by you shall be dual-licensed as above, without any additional terms or conditions.

atm90e32-async 0.2.1