nRF52xxx spi.TX and empty parameter causes invalid operation #3868
Description
When using empty parameter for spi.TX, previous TXD/RXD.MAXCNT values are not reseted and causes weird operations depending what was done before. Fixing is easy and tested to work with nRF52833.
File machine_nrf52xxx.go, line 291 and forward:
if len(r) != 0 {
spi.Bus.RXD.PTR.Set(uint32(uintptr(unsafe.Pointer(&r[0]))))
n := uint32(len(r))
if n > 255 {
n = 255
}
spi.Bus.RXD.MAXCNT.Set(n)
r = r[n:]
}
if len(w) != 0 {
spi.Bus.TXD.PTR.Set(uint32(uintptr(unsafe.Pointer(&w[0]))))
n := uint32(len(w))
if n > 255 {
n = 255
}
spi.Bus.TXD.MAXCNT.Set(n)
w = w[n:]
}
Change to:
if len(r) != 0 {
spi.Bus.RXD.PTR.Set(uint32(uintptr(unsafe.Pointer(&r[0]))))
n := uint32(len(r))
if n > 255 {
n = 255
}
spi.Bus.RXD.MAXCNT.Set(n)
r = r[n:]
} else {
spi.Bus.RXD.MAXCNT.Set(0)
}
if len(w) != 0 {
spi.Bus.TXD.PTR.Set(uint32(uintptr(unsafe.Pointer(&w[0]))))
n := uint32(len(w))
if n > 255 {
n = 255
}
spi.Bus.TXD.MAXCNT.Set(n)
w = w[n:]
} else {
spi.Bus.TXD.MAXCNT.Set(0)
}