I2C

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Handle

use lager::LagerBox;

let lager = LagerBox::from_env()?;
let bus = lager.i2c("i2c1");

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Methods

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Types

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I2cEffectiveConfig

pub struct I2cEffectiveConfig {
    pub frequency_hz: Option<i64>,
    pub pull_ups: Option<bool>,
}

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Method Reference

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configure(frequency_hz: Option<u32>, pull_ups: Option<bool>) -> Result<I2cEffectiveConfig>

let cfg = bus.configure(Some(400_000), Some(true))?;
println!("{:?} Hz, pull-ups {:?}", cfg.frequency_hz, cfg.pull_ups);

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scan() -> Result<Vec<u16>>

for addr in bus.scan()? {
    println!("device at 0x{addr:02x}");
}

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scan_range(start_addr: u16, end_addr: u16) -> Result<Vec<u16>>

let found = bus.scan_range(0x40, 0x50)?;

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read(address: u16, num_bytes: u32) -> Result<Vec<u8>>

let bytes = bus.read(0x48, 2)?;

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write(address: u16, data: &[u8]) -> Result<()>

bus.write(0x48, &[0x01, 0x60])?;

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write_read(address: u16, data: &[u8], num_bytes: u32) -> Result<Vec<u8>>

// Point at register 0x00, then read two bytes from it.
let temp = bus.write_read(0x48, &[0x00], 2)?;

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Examples

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Discover what is on the bus, then read a sensor register

use lager::LagerBox;

let lager = LagerBox::from_env()?;
let bus = lager.i2c("i2c1");

bus.configure(Some(100_000), Some(true))?;

let addrs = bus.scan()?;
assert!(addrs.contains(&0x48), "temperature sensor missing; bus has {addrs:02x?}");

let raw = bus.write_read(0x48, &[0x00], 2)?;
let celsius = i16::from_be_bytes([raw[0], raw[1]]) as f64 / 256.0;
println!("{celsius:.2} C");

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Supported Hardware

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Notes

• Addresses are 7-bit. Pass 0x48, not the 8-bit read/write-shifted forms.
• A scan hit is not a promise. A scan reports which addresses acknowledged an address byte; a subsequent read() can still fail with No ACK from device at 0x48. This is common on a bus with the controller’s internal pull-ups disabled, where the line can float convincingly enough to look like an ACK. Treat scan() as discovery, not verification.
• Bus transactions run on the box under the physical device’s lock, so a write-then-read cannot be interleaved by another request on the same device.
• configure() persists. A frequency you set in one test is still set in the next.