src/libboard_artiq/src/drtioaux_proto.rs

@@ -47,6 +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 },
 
     SpiSetConfigRequest { destination: u8, busno: u8, flags: u8, length: u8, div: u8, cs: u8 },
     SpiWriteRequest { destination: u8, busno: u8, data: u32 },
@@ -152,6 +153,13 @@ impl Packet {
             0x87 => Packet::I2cBasicReply {
                 succeeded: reader.read_bool()?
             },
+            0x88 => Packet::I2cPca954xSelectRequest {
+                destination: reader.read_u8()?,
+                busno: reader.read_u8()?,
+                address: reader.read_u8()?,
+                channel: reader.read_u8()?,
+                clear: reader.read_bool()?
+            },
 
             0x90 => Packet::SpiSetConfigRequest {
                 destination: reader.read_u8()?,
@@ -301,6 +309,14 @@ impl Packet {
                 writer.write_u8(0x87)?;
                 writer.write_bool(succeeded)?;
             },
+            Packet::I2cPca954xSelectRequest { destination, busno, address, channel, clear } => {
+                writer.write_u8(0x88)?;
+                writer.write_u8(destination)?;
+                writer.write_u8(busno)?;
+                writer.write_u8(address)?;
+                writer.write_u8(channel)?;
+                writer.write_bool(clear)?;
+            },
 
             Packet::SpiSetConfigRequest { destination, busno, flags, length, div, cs } => {
                 writer.write_u8(0x90)?;

src/runtime/src/i2c.rs

@@ -60,6 +60,18 @@ pub extern fn read(busno: i32, ack: bool) -> i32 {
     }
 }
 
+pub extern fn pca954x_select(busno: i32, address: i32, channel: i32, clear: bool) {
+    if busno > 0 {
+        artiq_raise!("I2CError", "I2C bus could not be accessed");
+    }
+    unsafe {
+        let ch = if clear { None } else { Some(channel as u8) };
+        if (&mut I2C_BUS).as_mut().unwrap().pca954x_select(address as u8, ch).is_err() {
+            artiq_raise!("I2CError", "PCA954X select failed");
+        }
+    }
+}
+
 pub fn init() {
     let mut i2c = libboard_zynq::i2c::I2c::i2c0();
     i2c.init().expect("I2C bus initialization failed");

src/runtime/src/kernel/api.rs

@@ -116,6 +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),
 
         // Double-precision floating-point arithmetic helper functions
         // RTABI chapter 4.1.2, Table 2

src/satman/src/main.rs

@@ -282,6 +282,12 @@ 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 } => {
+            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();
+            drtioaux::send(0, &drtioaux::Packet::I2cBasicReply { succeeded: succeeded })
+        }
 
         drtioaux::Packet::SpiSetConfigRequest { destination: _destination, busno: _busno, 
                                                 flags: _flags, length: _length, div: _div, cs: _cs } => {