go-packages/go-rpio
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Use mash filter if it makes sense

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This commit is contained in:
Drahoslav 2017-11-16 01:14:01 +01:00
parent fd0764b709
commit 95bb91625f
1 changed files with 23 additions and 8 deletions
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31
rpio.go
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@ -306,11 +306,12 @@ func PullMode(pin Pin, pull Pull) {
// changing frequency for one pin will change it also for all pins within a group
// The groups are: clk0 (4, 20, 32, 34), clk1 (5, 21, 42, 43) and clk2 (6 and 43)
func SetFreq(pin Pin, freq int) {
const source = 19200000 // oscilator frequency
// TODO: would be nice to choose best clock source depending on target frequency, oscilator is used for now
const sourceFreq = 19200000 // oscilator frequency
const maxUint12 = 4095
divi := uint32(source / freq)
divf := uint32(((source % freq) << 12) / freq)
divi := uint32(sourceFreq / freq)
divf := uint32(((sourceFreq % freq) << 12) / sourceFreq)
divi &= maxUint12
divf &= maxUint12
@ -331,21 +332,35 @@ func SetFreq(pin Pin, freq int) {
return
}
mash := uint32(1 << 9) // 1-stage MASH
if divi < 2 || divf == 0 {
mash = 0
}
memlock.Lock()
defer memlock.Unlock()
const PASSWORD = 0x5A000000
const busy = 0x80
const enab = 0x10
const src = 0x01 // oscilator
const busy = 1 << 7
const enab = 1 << 4
const src = 1 << 0 // oscilator
clkMem[clkCtlReg] = PASSWORD | src // stop gpio clock
for clkMem[clkCtlReg]&busy != 0 {
} // ... and wait
time.Sleep(time.Microsecond * 10)
} // ... and wait for not busy
clkMem[clkCtlReg] = PASSWORD | mash | src // set mash and source (without enabling clock)
clkMem[clkDivReg] = PASSWORD | (divi << 12) | divf // set dividers
clkMem[clkCtlReg] = PASSWORD | enab | src // start clock
// mash and src can not be changed in same step as enab, to prevent lock-up and glitches
time.Sleep(time.Microsecond * 10) // ... so wait for them to take effect
clkMem[clkCtlReg] = PASSWORD | mash | src | enab // finally start clock
for clkMem[clkCtlReg]&busy == 0 {
time.Sleep(time.Microsecond * 10)
} // ... and wait for busy, just to be sure
}
// Open and memory map GPIO memory range from /dev/mem .