43 lines
1.5 KiB
Rust
43 lines
1.5 KiB
Rust
use embedded_hal::blocking::{delay::DelayMs, i2c::WriteRead};
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// The EEPROM is a variant without address bits, so the 3 LSB of this word are "dont-cares".
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const I2C_ADDR: u8 = 0x50;
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// The MAC address is stored in the last 6 bytes of the 256 byte address space.
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const MAC_POINTER: u8 = 0xFA;
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pub fn read_eui48<T>(i2c: &mut T, delay: &mut impl DelayMs<u8>) -> [u8; 6]
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where
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T: WriteRead,
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{
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let mut previous_read: Option<[u8; 6]> = None;
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// On Stabilizer v1.1 and earlier hardware, there is a fault where the I2C bus is not connected
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// to the CPU until the P12V0A rail enables, which can take many seconds, or may never come up
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// at all. During these transient turn-on conditions, we may fail the I2C read operation. To
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// accomodate this, we repeat the I2C read for a set number of attempts with a fixed delay
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// between them. Then, we wait for the bus to stabilize by waiting until the MAC address
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// read-out is identical for two consecutive reads.
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for _ in 0..40 {
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let mut buffer = [0u8; 6];
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if i2c
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.write_read(I2C_ADDR, &[MAC_POINTER], &mut buffer)
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.is_ok()
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{
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if let Some(old_read) = previous_read {
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if old_read == buffer {
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return buffer;
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}
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}
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previous_read.replace(buffer);
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} else {
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// Remove any pending previous read if we failed the last attempt.
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previous_read.take();
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}
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delay.delay_ms(100);
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}
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panic!("Failed to read MAC address");
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}
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