top/polysyn/tusb322i: enable VBUS when enumerating as Accessory/DebugDfp

gateware/src/top/polysyn/fw/src/main.rs

@@ -30,7 +30,7 @@ use tiliqua_hal::embedded_graphics::prelude::*;
 
 use opts::persistence::*;
 use hal::pca9635::Pca9635Driver;
-use hal::tusb322::{TUSB322Driver, TUSB322Mode, AttachedState};
+use hal::tusb322::{TUSB322Driver, TUSB322Mode, AttachedState, AccessoryType};
 
 use tiliqua_fw::wavetable;
 
@@ -365,6 +365,7 @@ fn main() -> ! {
         let mut last_jack = pmod.jack();
 
         let mut usb_cc_attached_as_src = false;
+        let mut last_attached_state = AttachedState::NotAttached;
 
         loop {
 
@@ -380,16 +381,28 @@ fn main() -> ! {
 
                 // Type-C hotplugging detection
                 //
-                // Only enable VBUS if the TUSB322 Type-C controller says we are attached as a source.
-                // This is an extra safeguard against applying VBUS if we're accidentally connecting host<->host.
+                // Only enable VBUS if the TUSB322 Type-C controller says we are attached as:
+                // - Attached.SRC
+                // - Attached.ACCESSORY && AccessoryType.DebugDfp
+                //
+                // It seems some USB-C adapters will enumerate as a DebugDfp accessory. Enabling VBUS
+                // is still safe in this situation, as we can only land in DebugDfp if the CC
+                // controller is sure we are a DFP. It's not sufficient to just check
+                // Attached.ACCESSORY as we could also enumerate as an UFP accessory against a host!
+                //
+                // This is essentially a safeguard against applying VBUS if we're accidentally connecting host<->host.
                 //
 
-                if let Ok(status) = tusb322.read_connection_status_control() {
-                    // Only update on valid reads to reduce risk of unintended toggling mid-stream
-                    let new_state = status.attached_state == AttachedState::AttachedSrc;
-                    if new_state != usb_cc_attached_as_src {
-                        info!("USB CC hotplug: {:?}", status);
-                        usb_cc_attached_as_src = new_state;
+                if let Ok(ctrl) = tusb322.read_connection_status_control() {
+                    if let Ok(conn) = tusb322.read_connection_status() {
+                        // Only update on valid reads to reduce risk of unintended toggling mid-stream
+                        if ctrl.attached_state != last_attached_state {
+                            info!("USB hotplug: {:?} | {:?}", ctrl, conn);
+                            last_attached_state = ctrl.attached_state;
+                        }
+                        let debug_dfp = (ctrl.attached_state == AttachedState::AttachedAccessory) &&
+                                        (conn.accessory == AccessoryType::DebugDfp);
+                        usb_cc_attached_as_src = ctrl.attached_state == AttachedState::AttachedSrc || debug_dfp;
                     }
                 }
                 let usb_vbus_enabled = usb_cc_attached_as_src && (app.ui.opts.misc.usb_host.value == UsbHost::On);