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//go:build rp2040
package machine
import (
"device/rp"
"runtime/volatile"
"unsafe"
)
// On some boards, the XOSC can take longer than usual to stabilize. On such
// boards, this is needed to avoid a hard fault on boot/reset. Refer to
// PICO_XOSC_STARTUP_DELAY_MULTIPLIER in the Pico SDK for additional details.
const XOSC_STARTUP_DELAY_MULTIPLIER = 64
type xoscType struct {
ctrl volatile.Register32
status volatile.Register32
dormant volatile.Register32
startup volatile.Register32
reserved [3]volatile.Register32
count volatile.Register32
}
var xosc = (*xoscType)(unsafe.Pointer(rp.XOSC))
// init initializes the crystal oscillator system.
//
// This function will block until the crystal oscillator has stabilised.
func (osc *xoscType) init() {
// Assumes 1-15 MHz input
if xoscFreq > 15 {
panic("xosc frequency cannot be greater than 15MHz")
}
osc.ctrl.Set(rp.XOSC_CTRL_FREQ_RANGE_1_15MHZ)
// Set xosc startup delay
delay := (((xoscFreq * MHz) / 1000) + 128) / 256 * XOSC_STARTUP_DELAY_MULTIPLIER
osc.startup.Set(uint32(delay))
// Set the enable bit now that we have set freq range and startup delay
osc.ctrl.SetBits(rp.XOSC_CTRL_ENABLE_ENABLE << rp.XOSC_CTRL_ENABLE_Pos)
// Wait for xosc to be stable
for !osc.status.HasBits(rp.XOSC_STATUS_STABLE) {
}
}
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