From 74d1df3ff0541a91ec0af296d8ab70b4085f2381 Mon Sep 17 00:00:00 2001 From: Sebastien Bourdeauducq Date: Wed, 7 Mar 2018 10:56:12 +0800 Subject: [PATCH] firmware: implement si5324 skew calibration --- artiq/firmware/libboard_artiq/si5324.rs | 75 ++++++++++++++++++++++++- artiq/firmware/satman/main.rs | 2 +- 2 files changed, 74 insertions(+), 3 deletions(-) diff --git a/artiq/firmware/libboard_artiq/si5324.rs b/artiq/firmware/libboard_artiq/si5324.rs index 2738bec71..9b93eae96 100644 --- a/artiq/firmware/libboard_artiq/si5324.rs +++ b/artiq/firmware/libboard_artiq/si5324.rs @@ -278,7 +278,78 @@ pub fn select_recovered_clock(rc: bool) -> Result<()> { } #[cfg(has_si_phaser)] -pub fn calibrate_skew() -> Result<()> { - // TODO: implement +fn phase_shift(direction: u8) { + unsafe { + csr::si_phaser::phase_shift_write(direction); + while csr::si_phaser::phase_shift_done_read() == 0 {} + } + // wait for the Si5324 loop to stabilize + clock::spin_us(500); +} + +#[cfg(has_si_phaser)] +fn get_phaser_sample() -> bool { + let mut sample = true; + for _ in 0..32 { + if unsafe { csr::si_phaser::sample_result_read() } == 0 { + sample = false; + } + } + sample +} + +#[cfg(has_si_phaser)] +const PS_MARGIN: u32 = 28; + +#[cfg(has_si_phaser)] +fn get_stable_phaser_sample() -> (bool, u32) { + let mut nshifts: u32 = 0; + loop { + let s1 = get_phaser_sample(); + for _ in 0..PS_MARGIN { + phase_shift(1); + } + let s2 = get_phaser_sample(); + for _ in 0..PS_MARGIN { + phase_shift(1); + } + let s3 = get_phaser_sample(); + nshifts += 2*PS_MARGIN; + if s1 == s2 && s2 == s3 { + for _ in 0..PS_MARGIN { + phase_shift(0); + } + nshifts -= PS_MARGIN; + return (s2, nshifts); + } + } +} + +#[cfg(has_si_phaser)] +pub fn calibrate_skew(skew: u16) -> Result<()> { + // Get into a 0 region + let (s1, mut nshifts) = get_stable_phaser_sample(); + if s1 { + while get_phaser_sample() { + phase_shift(1); + nshifts += 1; + } + for _ in 0..PS_MARGIN { + phase_shift(1); + } + nshifts += PS_MARGIN; + } + + // Get to the 0->1 transition + while !get_phaser_sample() { + phase_shift(1); + nshifts += 1; + } + info!("nshifts to 0->1 siphaser transition: {} ({}deg)", nshifts, nshifts*360/(56*8)); + + // Apply specified skew referenced to that transition + for _ in 0..skew { + phase_shift(1); + } Ok(()) } diff --git a/artiq/firmware/satman/main.rs b/artiq/firmware/satman/main.rs index e1b60179d..19f0d2517 100644 --- a/artiq/firmware/satman/main.rs +++ b/artiq/firmware/satman/main.rs @@ -236,7 +236,7 @@ fn startup() { } info!("link is up, switching to recovered clock"); si5324::select_recovered_clock(true).expect("failed to switch clocks"); - si5324::calibrate_skew().expect("failed to calibrate skew"); + si5324::calibrate_skew(32).expect("failed to calibrate skew"); drtio_reset(false); drtio_reset_phy(false); while drtio_link_rx_up() {