1. I need to interface STM8S003F3 with WS2811. I want to know if external crystal is required for it or not, as WS2811 has very tight timings. I prefer to generate timing through NOP's for delay using inline functions

2. As STM8S003F3, Accuracy of Internal oscillator = +-5% over all temperature ranges.

3. WS2811 specifies:
a) T0H = 0.5μs ±150ns
b) T1H = 1.2μs ±150ns
c) T0L = 2.0μs ±150ns
d) T1L = 1.3μs ±150ns
e) RES = Above 50μs

4. With 16Mhz crystal, time for NOP is 1/16Mhz = 0.0625us
With on left end of accuracy -5%, time for NOP is 1/(16*.95) = 65.79ns
With on right end of accuracy +5%, time for NOP is 1/(16*1.05) = 59.52ns

5. Are below calculations for NOP's are ok? I think internal oscillator can also be used.

6. a) T0H = 0.5μs ±150ns
variation allowed around 0.5us is +-150ns i.e = 0.35us to 0.65us

NOP's in T0H = 0.5μs / 0.0625us = 8
Taking 8 NOP will generate = 0.5us
variation with +5% accuracy = 8 * 59.52ns = 0.476us
variation with -5% accuracy = 8 * 65.79ns = 0.526us

So well within specs here

b) T1H = 1.2μs ±150ns
variation allowed around 1.2us is +-150ns i.e = 1.05us to 1.35us

NOP's in T1H = 1.2μs / 0.0625us = 19.2
Taking 19 NOP will generate = 1.1875us
variation with +5% accuracy = 19 * 59.52ns = 1.131us
variation with -5% accuracy = 19 * 65.79ns = 1.25us

So well within specs here

c) T0L = 2.0μs ±150ns
variation allowed around 2.0us is +-150ns i.e = 1.85us to 2.15us

NOP's in T0L = 2.0μs / 0.0625us = 32
Taking 32 NOP will generate = 2.0μs
variation with +5% accuracy = 32 * 59.52ns = 1.905us
variation with -5% accuracy = 32 * 65.79ns = 2.105us

So well within specs here

d) T1L = 1.3μs ±150ns
variation allowed around 1.3us is +-150ns i.e = 1.15us to 1.45us

NOP's in T1L = 1.3μs / 0.0625us = 20.8
Taking 21 NOP will generate = 1.3125μs
variation with +5% accuracy = 21 * 59.52ns = 1.25us
variation with -5% accuracy = 21 * 65.79ns = 1.382us

So well within specs here

e) RES = Above 50μs
So number of NOP's should be so that,
at minimum clock time it should have at-least 50us
i.e 50us / 59.52ns = 840 NOP'should

Time for 840 NOP's at Min time 59.52ns = 840 * 59.52ns = 50us
Time for 840 NOP's at nom time 62.5ns = 840 * 62.5ns = 52.5us
Time for 840 NOP's at max time 65.79ns = 840 * 65.79ns = 55.263us

 

What is your final solution??

 

That hard to do it takes a 20 mhz crystal to bit bang. With a pic
This Is at 48 I ran out of room on a

But that chip maybe not have a problem It's like 1.6 cycles per instruction the pic's are 4