diff --git a/src/libboard_artiq/src/drtioaux_proto.rs b/src/libboard_artiq/src/drtioaux_proto.rs
index 3cc8118..c83da1d 100644
--- a/src/libboard_artiq/src/drtioaux_proto.rs
+++ b/src/libboard_artiq/src/drtioaux_proto.rs
@@ -47,7 +47,7 @@ pub enum Packet {
     I2cReadRequest { destination: u8, busno: u8, ack: bool },
     I2cReadReply { succeeded: bool, data: u8 },
     I2cBasicReply { succeeded: bool },
-    I2cPca954xSelectRequest { destination: u8, busno: u8, address: u8, channel: u8, clear: bool },
+    I2cSwitchSelectRequest { destination: u8, busno: u8, address: u8, mask: u8 },
 
     SpiSetConfigRequest { destination: u8, busno: u8, flags: u8, length: u8, div: u8, cs: u8 },
     SpiWriteRequest { destination: u8, busno: u8, data: u32 },
@@ -153,12 +153,11 @@ impl Packet {
             0x87 => Packet::I2cBasicReply {
                 succeeded: reader.read_bool()?
             },
-            0x88 => Packet::I2cPca954xSelectRequest {
+            0x88 => Packet::I2cSwitchSelectRequest {
                 destination: reader.read_u8()?,
                 busno: reader.read_u8()?,
                 address: reader.read_u8()?,
-                channel: reader.read_u8()?,
-                clear: reader.read_bool()?
+                mask: reader.read_u8()?
             },
 
             0x90 => Packet::SpiSetConfigRequest {
@@ -309,13 +308,12 @@ impl Packet {
                 writer.write_u8(0x87)?;
                 writer.write_bool(succeeded)?;
             },
-            Packet::I2cPca954xSelectRequest { destination, busno, address, channel, clear } => {
+            Packet::I2cPca954xSelectRequest { destination, busno, address, mask } => {
                 writer.write_u8(0x88)?;
                 writer.write_u8(destination)?;
                 writer.write_u8(busno)?;
                 writer.write_u8(address)?;
-                writer.write_u8(channel)?;
-                writer.write_bool(clear)?;
+                writer.write_u8(mask)?;
             },
 
             Packet::SpiSetConfigRequest { destination, busno, flags, length, div, cs } => {
diff --git a/src/runtime/src/i2c.rs b/src/runtime/src/i2c.rs
index 42f19a9..b2c166f 100644
--- a/src/runtime/src/i2c.rs
+++ b/src/runtime/src/i2c.rs
@@ -60,14 +60,25 @@ pub extern fn read(busno: i32, ack: bool) -> i32 {
     }
 }
 
-pub extern fn pca954x_select(busno: i32, address: i32, channel: i32, clear: bool) {
+pub extern fn switch_select(busno: i32, address: i32, mask: i32) {
     if busno > 0 {
         artiq_raise!("I2CError", "I2C bus could not be accessed");
     }
     unsafe {
-        let ch = if clear { None } else { Some(channel as u8) };
+        let ch = match mask { //decode from mainline, PCA9548-centric API
+            0x00 => None,
+            0x01 => Some(0),
+            0x02 => Some(1),
+            0x04 => Some(2),
+            0x08 => Some(3),
+            0x10 => Some(4),
+            0x20 => Some(5),
+            0x40 => Some(6),
+            0x80 => Some(7),
+            _ => { artiq_raise!("I2CError", "switch select supports only one channel"); return }
+        };
         if (&mut I2C_BUS).as_mut().unwrap().pca954x_select(address as u8, ch).is_err() {
-            artiq_raise!("I2CError", "PCA954X select failed");
+            artiq_raise!("I2CError", "switch select failed");
         }
     }
 }
diff --git a/src/runtime/src/kernel/api.rs b/src/runtime/src/kernel/api.rs
index bf07008..122c7bb 100644
--- a/src/runtime/src/kernel/api.rs
+++ b/src/runtime/src/kernel/api.rs
@@ -116,7 +116,7 @@ pub fn resolve(required: &[u8]) -> Option<u32> {
         api!(i2c_stop = i2c::stop),
         api!(i2c_write = i2c::write),
         api!(i2c_read = i2c::read),
-        api!(i2c_pca954x_select = i2c::pca954x_select),
+        api!(i2c_switch_select = i2c::switch_select),
 
         // Double-precision floating-point arithmetic helper functions
         // RTABI chapter 4.1.2, Table 2
diff --git a/src/satman/src/main.rs b/src/satman/src/main.rs
index 1a75e64..f8915d7 100644
--- a/src/satman/src/main.rs
+++ b/src/satman/src/main.rs
@@ -282,10 +282,21 @@ fn process_aux_packet(_repeaters: &mut [repeater::Repeater],
                     &drtioaux::Packet::I2cReadReply { succeeded: false, data: 0xff })
             }
         }
-        drtioaux::Packet::I2cStartRequest { destination: _destination, busno: _busno, address, channel, clear } => {
+        drtioaux::Packet::I2cSwitchSelectRequest { destination: _destination, busno: _busno, address, mask } => {
             forward!(_routing_table, _destination, *_rank, _repeaters, &packet, timer);
-            let ch = if clear { None } else { Some(channel as u8) };
-            let succeeded = i2c.pca954x_select(address, channel).is_ok();
+            ch = match mask { //decode from mainline, PCA9548-centric API
+                0x00 => None,
+                0x01 => Some(0),
+                0x02 => Some(1),
+                0x04 => Some(2),
+                0x08 => Some(3),
+                0x10 => Some(4),
+                0x20 => Some(5),
+                0x40 => Some(6),
+                0x80 => Some(7),
+                _ => { return drtioaux::send(0, &drtioaux::Packet::I2cBasicReply { succeeded: false }); }
+            };
+            let succeeded = i2c.pca954x_select(address, ch).is_ok();
             drtioaux::send(0, &drtioaux::Packet::I2cBasicReply { succeeded: succeeded })
         }