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machine: add USBDevice.Attach and USBDevice.Detach #5563

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14 changes: 14 additions & 0 deletions src/machine/machine_atsamd21_usb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,20 @@ func (dev *USBDevice) Configure(config UARTConfig) {
dev.initcomplete = true
}

// Attach connects the device to the USB bus, allowing the host to detect and
// enumerate it. It can be used together with Detach to delay enumeration
// until the USB configuration (device identifiers, classes, ...) is complete.
func (dev *USBDevice) Attach() {
sam.USB_DEVICE.CTRLB.ClearBits(sam.USB_DEVICE_CTRLB_DETACH)
}

// Detach disconnects the device from the USB bus. To the host this appears
// as if the device was unplugged. A subsequent Attach makes the host
// enumerate the device again.
func (dev *USBDevice) Detach() {
sam.USB_DEVICE.CTRLB.SetBits(sam.USB_DEVICE_CTRLB_DETACH)
}

func handlePadCalibration() {
// Load Pad Calibration data from non-volatile memory
// This requires registers that are not included in the SVD file.
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14 changes: 14 additions & 0 deletions src/machine/machine_atsamd51_usb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,20 @@ func (dev *USBDevice) Configure(config UARTConfig) {
dev.initcomplete = true
}

// Attach connects the device to the USB bus, allowing the host to detect and
// enumerate it. It can be used together with Detach to delay enumeration
// until the USB configuration (device identifiers, classes, ...) is complete.
func (dev *USBDevice) Attach() {
sam.USB_DEVICE.CTRLB.ClearBits(sam.USB_DEVICE_CTRLB_DETACH)
}

// Detach disconnects the device from the USB bus. To the host this appears
// as if the device was unplugged. A subsequent Attach makes the host
// enumerate the device again.
func (dev *USBDevice) Detach() {
sam.USB_DEVICE.CTRLB.SetBits(sam.USB_DEVICE_CTRLB_DETACH)
}

func handlePadCalibration() {
// Load Pad Calibration data from non-volatile memory
// This requires registers that are not included in the SVD file.
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15 changes: 15 additions & 0 deletions src/machine/machine_nrf52840_usb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -89,6 +89,21 @@ func (dev *USBDevice) Configure(config UARTConfig) {
dev.initcomplete = true
}

// Attach connects the device to the USB bus by enabling the DP pull-up,
// allowing the host to detect and enumerate it. It can be used together with
// Detach to delay enumeration until the USB configuration (device
// identifiers, classes, ...) is complete.
func (dev *USBDevice) Attach() {
nrf.USBD.USBPULLUP.Set(1)
}

// Detach disconnects the device from the USB bus by disabling the DP pull-up.
// To the host this appears as if the device was unplugged. A subsequent
// Attach makes the host enumerate the device again.
func (dev *USBDevice) Detach() {
nrf.USBD.USBPULLUP.Set(0)
}

func handleUSBIRQ(interrupt.Interrupt) {
if nrf.USBD.EVENTS_SOF.Get() == 1 {
nrf.USBD.EVENTS_SOF.Set(0)
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15 changes: 15 additions & 0 deletions src/machine/machine_rp2040_usb.go
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Expand Up @@ -46,6 +46,21 @@ func (dev *USBDevice) Configure(config UARTConfig) {
rp.USBCTRL_REGS.SIE_CTRL.SetBits(rp.USBCTRL_REGS_SIE_CTRL_PULLUP_EN)
}

// Attach connects the device to the USB bus by enabling the DP pull-up,
// allowing the host to detect and enumerate it. It can be used together with
// Detach to delay enumeration until the USB configuration (device
// identifiers, classes, ...) is complete.
func (dev *USBDevice) Attach() {
rp.USBCTRL_REGS.SIE_CTRL.SetBits(rp.USBCTRL_REGS_SIE_CTRL_PULLUP_EN)

@rdon-key rdon-key Jul 28, 2026

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RP2040/RP2350 provide atomic bitmask set/clear aliases at +0x2000 and
+0x3000 (RP2040 datasheet 2.1.2, p.18:
https://datasheets.raspberrypi.com/rp2040/rp2040-datasheet.pdf), which
modify only the selected bits. SIE_CTRL is also touched from the ISR,
so this avoids the read-modify-write. Could we use those aliases here
for PULLUP_EN?

@sago35 sago35 Jul 28, 2026

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Thanks for the great suggestion. I think we can definitely use it here, but it would probably be better handled in a separate PR—for example, by integrating it into implementations like SetBits() / ClearBits()/ ....

However, this suggested approach might only work for registers and not for standard RAM. If that’s the case, we might need to consider a slightly more complex approach.

Since that change would have a broad impact, it's likely better to target the dev branch right after the upcoming release, rather than squeezing it into TinyGo 0.42.

Would you be open to creating a separate PR for that?

@sago35 sago35 Jul 28, 2026

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I created Issue #5564

@rdon-key rdon-key Jul 29, 2026 •
edited
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Understood. I'll look into a more general solution, although it may take some time.

For this PR, could we keep the change local and use the atomic aliases directly?

For example:

// USBCTRL_REGS aliases for atomic bitmask set/clear (datasheet section 2.1.2).
var (
	usbSet = (*rp.USBCTRL_REGS_Type)(unsafe.Pointer(
		uintptr(unsafe.Pointer(rp.USBCTRL_REGS)) + 0x2000))
	usbClr = (*rp.USBCTRL_REGS_Type)(unsafe.Pointer(
		uintptr(unsafe.Pointer(rp.USBCTRL_REGS)) + 0x3000))
)

func (dev *USBDevice) Attach() {
	usbSet.SIE_CTRL.Set(rp.USBCTRL_REGS_SIE_CTRL_PULLUP_EN)
}

func (dev *USBDevice) Detach() {
	usbClr.SIE_CTRL.Set(rp.USBCTRL_REGS_SIE_CTRL_PULLUP_EN)
}

And similarly for RP2350.

@sago35 sago35 Jul 29, 2026

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I don't think there is a need to change to a new method in this PR.

This code is a new change and has no impact on other parts. Furthermore, by using SetBits() and similar functions, the internal implementation will be updated to a better form. There is no reason to leave open the possibility of an implementation that differs from the future SetBits().

@rdon-key rdon-key Jul 30, 2026

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Thanks. Understood. I still think this should use the atomic write even temporarily, but it's your call.

}

// Detach disconnects the device from the USB bus by disabling the DP pull-up.
// To the host this appears as if the device was unplugged. A subsequent
// Attach makes the host enumerate the device again.
func (dev *USBDevice) Detach() {
rp.USBCTRL_REGS.SIE_CTRL.ClearBits(rp.USBCTRL_REGS_SIE_CTRL_PULLUP_EN)
}

func handleUSBIRQ(intr interrupt.Interrupt) {
status := rp.USBCTRL_REGS.INTS.Get()

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15 changes: 15 additions & 0 deletions src/machine/machine_rp2350_usb.go
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,21 @@ func (dev *USBDevice) Configure(config UARTConfig) {
rp.USB.SetMAIN_CTRL_PHY_ISO(0x0)
}

// Attach connects the device to the USB bus by enabling the DP pull-up,
// allowing the host to detect and enumerate it. It can be used together with
// Detach to delay enumeration until the USB configuration (device
// identifiers, classes, ...) is complete.
func (dev *USBDevice) Attach() {
rp.USB.SIE_CTRL.SetBits(rp.USB_SIE_CTRL_PULLUP_EN)
}

// Detach disconnects the device from the USB bus by disabling the DP pull-up.
// To the host this appears as if the device was unplugged. A subsequent
// Attach makes the host enumerate the device again.
func (dev *USBDevice) Detach() {
rp.USB.SIE_CTRL.ClearBits(rp.USB_SIE_CTRL_PULLUP_EN)
}

func handleUSBIRQ(intr interrupt.Interrupt) {
status := rp.USB.INTS.Get()

Expand Down
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