ws2812 vhdl problemHi there, I tried to run vhdl code from https://github.com/trobanga/ws2812/blob/master/ws2812.vhdl The strange thing is that timings are not met. As described in code, i connect 50mhz clock to the ip block. Can someone give me a hand with this and test vhdl code? Results attached. Many thanks, FlatByte
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Flat B. wrote: > i connect 50mhz milli Hertz? > The strange thing is that timings are not met. As far as I see the timing is exactly as to be expected. 350ns are not possible with 20ns granularity, therefore the term g_T0H * CLOCK_FREQ / 1000 results in a time of 340ns. And the additional 40ns are due to the state transitions wh and wl in the FSM, so you must get 340ns+20ns+800ns+20ns = 1180ns and 600ns+20ns+700ns+20ns = 1340ns with this code. > The strange thing is that timings are not met. What timing does a behavioural simulation show? I had 5 spare minutes, did a short behavioural simulation of that code and it looks like your measurement. So that turns out the question: whats the actual problem?
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Wow, many thanks for the great discussion. At last I've found right place and right people for VHDL/FPGA discussion. Lothar M. wrote: > Flat B. wrote: > > > i connect 50mhz > > milli Hertz? Right. MHz. Lothar M. wrote: > The strange thing is that timings are not met. > As far as I see the timing is exactly as to be expected. > 350ns are not possible with 20ns granularity, therefore the term g_T0H * > CLOCK_FREQ / 1000 results in a time of 340ns. And the additional 40ns > are due to the state transitions wh and wl in the FSM, so you must get > 340ns+20ns+800ns+20ns = 1180ns and 600ns+20ns+700ns+20ns = 1340ns with > this code. Wow. Thanks! Lothar M. wrote: > So that turns out the question: whats the actual problem? As a "new" in VHDL/FPGA I was almost sure I did something wrong implementing ws2812.vhdl file. I expected 800khz for driving WS2812B leds. Once again - many thanks! Your responses confirms that ws2812.vhdl doesn't generate 800 KHz pulse. PS. ws2812.vhdl file is not mine - I've just found it on the internet. Flat B. wrote: > I expected 800khz for driving WS2812B leds. According to the timing spec in the datasheet the solution is fine. 800kHz are onla a "typical" value. Its just the reciprocal value of the TH+TL=1.25μs, ignoring the ±600ns which results in 540kHz...1.5MHz.
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