diff --git a/artiq/firmware/libboard_artiq/hmc542.rs b/artiq/firmware/libboard_artiq/hmc542.rs
new file mode 100644
index 000000000..70cd8af54
--- /dev/null
+++ b/artiq/firmware/libboard_artiq/hmc542.rs
@@ -0,0 +1,54 @@
+use board::{csr, clock};
+
+const PIN_LE:    u32 = 1 << 0;
+const PIN_SIN:   u32 = 1 << 1;
+const PIN_CLK:   u32 = 1 << 2;
+const PIN_RST_N: u32 = 1 << 3;
+const PIN_RST:   u32 = PIN_RST_N;
+
+const CARDS:    usize = 4;
+const CHANNELS: usize = 2;
+
+fn set_pins(card_index: usize, chan_index: usize, pins: u32) {
+    let pins = pins ^ PIN_RST_N;
+    let shift = card_index * 2 + chan_index;
+    unsafe {
+        let state = csr::allaki_atts::out_read();
+        let state = state & !(0xf << shift);
+        let state = state | (pins << shift);
+        csr::allaki_atts::out_write(state);
+    }
+    clock::spin_us(100);
+}
+
+/// Attenuation is in units of 0.5dB, from 0dB (0) to 31.5dB (63).
+pub fn program(card_index: usize, chan_index: usize, atten: u8) {
+    assert!(card_index < 4 && chan_index < 2);
+
+    // 0b111111 = 1dB
+    // 0b111110 = 0.5dB
+    // 0b111101 = 1dB
+    // ...
+    // 0b011111 = 16dB
+    // 0b000000 = 31.5dB
+    let atten = !(atten << 2);
+
+    let set_pins = |pins| set_pins(card_index, chan_index, pins);
+    set_pins(PIN_RST);
+    set_pins(0);
+    for n in 0..8 {
+        let sin = if atten & 1 << n != 0 { PIN_SIN } else { 0 };
+        set_pins(sin);
+        set_pins(sin | PIN_CLK);
+    }
+    set_pins(PIN_LE);
+}
+
+/// See `program`.
+pub fn program_all(atten: u8) {
+    for card in 0..CARDS {
+        for chan in 0..CHANNELS {
+            program(card, chan, atten)
+        }
+    }
+}
diff --git a/artiq/firmware/libboard_artiq/lib.rs b/artiq/firmware/libboard_artiq/lib.rs
index 3307681b3..127a55db8 100644
--- a/artiq/firmware/libboard_artiq/lib.rs
+++ b/artiq/firmware/libboard_artiq/lib.rs
@@ -23,3 +23,5 @@ pub mod hmc830_7043;
 mod ad9154_reg;
 #[cfg(has_ad9154)]
 pub mod ad9154;
+#[cfg(has_allaki_atts)]
+pub mod hmc542;
diff --git a/artiq/firmware/runtime/main.rs b/artiq/firmware/runtime/main.rs
index 378d44f07..6ce66595c 100644
--- a/artiq/firmware/runtime/main.rs
+++ b/artiq/firmware/runtime/main.rs
@@ -95,6 +95,8 @@ fn startup() {
     board_artiq::hmc830_7043::init().expect("cannot initialize HMC830/7043");
     #[cfg(has_ad9154)]
     board_artiq::ad9154::init().expect("cannot initialize AD9154");
+    #[cfg(has_allaki_atts)]
+    board_artiq::hmc542::program_all(8/*=4dB*/);
 
     #[cfg(has_ethmac)]
     startup_ethernet();