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atsamd5x: improve USBCDC #1452

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atsamd5x: improve USBCDC #1452

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69 changes: 50 additions & 19 deletions src/machine/machine_atsamd51.go
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Original file line number Diff line number Diff line change
Expand Up @@ -902,7 +902,10 @@ type UART struct {

var (
// UART0 is actually a USB CDC interface.
UART0 = USBCDC{Buffer: NewRingBuffer()}
UART0 = USBCDC{
Buffer: NewRingBuffer(),
TxBuffer: NewRingBuffer(),
}
)

const (
Expand Down Expand Up @@ -1708,33 +1711,55 @@ func (pwm PWM) getMux() PinMode {

// USBCDC is the USB CDC aka serial over USB interface on the SAMD21.
type USBCDC struct {
Buffer *RingBuffer
Buffer *RingBuffer
TxBuffer *RingBuffer
waitTxc bool
}

// WriteByte writes a byte of data to the USB CDC interface.
func (usbcdc USBCDC) WriteByte(c byte) error {
// Supposedly to handle problem with Windows USB serial ports?
// Flush flushes buffered data.
func (usbcdc *USBCDC) Flush() error {
if usbLineInfo.lineState > 0 {
// set the data
udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN][0] = c
sz := usbcdc.TxBuffer.Used()
if 0 < sz {

usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN]))))
if usbcdc.waitTxc {
// waiting for the next flush(), because the transmission is not complete
return nil
}
usbcdc.waitTxc = true

// clean multi packet size of bytes already sent
usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].PCKSIZE.ClearBits(usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Mask << usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Pos)
// set the data
for i := uint8(0); i < sz; i++ {
udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN][i], _ = usbcdc.TxBuffer.Get()
}
Comment on lines +1732 to +1734
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@sago35 sago35 Nov 2, 2020

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This process is a byte copy, but it's a waste of time.
I will create a new PR that improves on this part of the process.

usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].ADDR.Set(uint32(uintptr(unsafe.Pointer(&udd_ep_in_cache_buffer[usb_CDC_ENDPOINT_IN]))))

// set count of bytes to be sent
usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].PCKSIZE.SetBits((1 & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos)
// clean multi packet size of bytes already sent
usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].PCKSIZE.ClearBits(usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Mask << usb_DEVICE_PCKSIZE_MULTI_PACKET_SIZE_Pos)

// clear transfer complete flag
setEPINTFLAG(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1)
// set count of bytes to be sent
usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].PCKSIZE.ClearBits(usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos)
usbEndpointDescriptors[usb_CDC_ENDPOINT_IN].DeviceDescBank[1].PCKSIZE.SetBits((uint32(sz) & usb_DEVICE_PCKSIZE_BYTE_COUNT_Mask) << usb_DEVICE_PCKSIZE_BYTE_COUNT_Pos)

// send data by setting bank ready
setEPSTATUSSET(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPSTATUSSET_BK1RDY)
// clear transfer complete flag
setEPINTFLAG(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1)

// wait for transfer to complete
timeout := 3000
for (getEPINTFLAG(usb_CDC_ENDPOINT_IN) & sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1) == 0 {
// send data by setting bank ready
setEPSTATUSSET(usb_CDC_ENDPOINT_IN, sam.USB_DEVICE_ENDPOINT_EPSTATUSSET_BK1RDY)
}
}
return nil
}

// WriteByte writes a byte of data to the USB CDC interface.
func (usbcdc USBCDC) WriteByte(c byte) error {
// Supposedly to handle problem with Windows USB serial ports?
if usbLineInfo.lineState > 0 {
// `timeout == 10000` waits for a bit over 1ms (120MHz)
timeout := 10000
ok := false
for !ok {
ok = usbcdc.TxBuffer.Put(c)
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@sago35 sago35 Nov 2, 2020

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RingBuffer.Put() does not consider calling from multiple priorities.
interrupt.Disable() is required.

timeout--
if timeout == 0 {
return errUSBCDCWriteByteTimeout
Expand Down Expand Up @@ -1946,9 +1971,15 @@ func handleUSBIRQ(interrupt.Interrupt) {
case usb_CDC_ENDPOINT_IN, usb_CDC_ENDPOINT_ACM:
setEPSTATUSCLR(i, sam.USB_DEVICE_ENDPOINT_EPSTATUSCLR_BK1RDY)
setEPINTFLAG(i, sam.USB_DEVICE_ENDPOINT_EPINTFLAG_TRCPT1)

if i == usb_CDC_ENDPOINT_IN {
UART0.waitTxc = false
}
}
}
}

UART0.Flush()
}

func initEndpoint(ep, config uint32) {
Expand Down