Running PIO flat out?

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Bleep
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Posted: 03:28pm 30 Jan 2025      

A question for our resident PIO experts, probably Peter or Harm.
I've just splashed out on a second hand 200MHz Oscilloscope and I'm trying to generate a 200MHz signal, or there about to test it with.
I have managed to use the Pico SDK to build an executable, which is overclocked to 428MHz toggling a GPIO pin flat out, I get a nice 107MHz signal, which the scope displays fine. (zip file below)
Is there a way of getting the PIO under MMBasic to do something similar, preferably higher frequency, closer to 200MHz. Even better a variable frequency, up to as high as possible. I realise the step size is likely to be relatively large, but a selection of test frequencies would be nice? maybe a selection of power of 2 frequencies on adjacent pins? Any thoughts?
Thanks in anticipation. :-) Kevin.
FastToggle.zip
Mixtel90

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Posted: 03:49pm 30 Jan 2025      

At full speed a PIO state machine can carry out 1 instruction per CPU clock cycle. I suppose that will mean one instruction to set a pin, one to reset it and one to jump back to the first instruction. That would, I think, give a pin that clocked at a maximum of CLK/3 Hz. 142.66MHz.

Now, there are instructions that can actually do two things in one clock cycle (side set etc.). I'm not well up enough on the PIO to be able to help there. It could be that the reset and jump back could be combined.

Note. If a state machine hits the end of it's memory area it automatically jumps back to its start point, so if you put the set instruction at the start point and the end instruction as the last instruction in memory it should toggle at CLK/2, I think.

.
Edited 2025-01-31 01:52 by Mixtel90
Volhout
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Posted: 03:59pm 30 Jan 2025      

Hi Kevin,

Here you go. This toggles GP0 at half the PIO clock speed.
Change the f0 value according your wishes.

 setpin gp0,PIO1
   
 PIO ASSEMBLE 1,".program toggle"
 pio assemble 1,".line 0"         'start line 0
 PIO ASSEMBLE 1,"set pindirs,1"   'set GPIO to output
 PIO ASSEMBLE 1,".wrap target"
 PIO ASSEMBLE 1,"set pins,0"      'set low
 PIO ASSEMBLE 1,"set pins,1"      'set high
 PIO ASSEMBLE 1,".wrap"           'wrap back to wrap_target
 PIO ASSEMBLE 1,".end program list"
 
 'configure pio1 StateMachine 0
 f0 = 133e6    '1MHz, change this to meet your need
 '              a b c d e f g   'a,e=side set   c,g=OUT  b,f=set
 p0 = Pio(PINCTRL 0,1,,,,GP0,)                  
 e0 = Pio(EXECCTRL GP0,Pio(.wrap target),Pio(.wrap))
 
 'write the configuration
 PIO init machine 1,0,f0,p0,e0,,0        'SM0 start at address 0
 PIO START 1,0
 
 do:loop


Theoretically you can set the PIO clock frequency to the same value as the ARM speed.
But if PIO can really do 400MHz I am not sure. Try it.
Another problem may be the IO pin that cannot toggle fast enough. At 200MHz, you may see a sine wave half the 3.3V amplitude. Becuase that is all the IO pin silicon can do.

Volhout

P.S. if you want to use a different GPIO pin, change the GP0 in PINCTRL. The one in EXECCTRL is a dummy, and can stay the same.
Edited 2025-01-31 02:14 by Volhout
Mixtel90

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Posted: 04:19pm 30 Jan 2025      

Ah, that is the question! Can you get 400MHz out of a component specified at a normal speed of 150MHz?  :)
Bleep
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Posted: 04:33pm 30 Jan 2025      

Hi Harm,
That was quick, I'll give it a go. Thanks very much. :-)

Hi Mick,
I only need it to do 200Mhz, but even at 107, it's already fairly sinusoidal, so it may/or not cope.
Regards Kevin.
Mixtel90

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Posted: 05:00pm 30 Jan 2025      

Have you set up your probe using the square wave from the scope? Better check it anyway. Also, with those edge times, you need the short GND wire from the probe tip.
Edited 2025-01-31 03:01 by Mixtel90
PhenixRising
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Posted: 07:44pm 30 Jan 2025      

I wonder if a 74HC14 Schmitt-Trigger would help?
phil99

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Posted: 08:55pm 30 Jan 2025      

It may help, especially if the 74HC14 is close to the Pico.
The output resistance of the Pico pins is 40 - 50Ω so driving the scope input capacitance may contribute to the rounding.

Edit.
An odd thing.
Tried the program above but using FIN to show the output (Pico2 VGA beta 5) and the Pico freezes when PIO output is connected to FIN. Unplug the link and it resumes running.

Tried various CPU speeds, PIO speeds and FIN sampling times but always same result.
> option list
PicoMiteVGA MMBasic RP2350A Edition V6.00.02b5
OPTION SYSTEM I2C GP14,GP15
OPTION FLASH SIZE 4194304
OPTION COLOURCODE ON
OPTION KEYBOARD US
OPTION DEFAULT MODE 3
OPTION DISPLAY 60, 133
OPTION SDCARD GP13, GP10, GP11, GP12
> RUN
0: E081
1: E000
2: E001
0
0   <---------Heartbeat and program stop when GP0 linked to GP7, resume when removed
0
0
0
>
> LIST
SetPin gp7,FIN,10
SetPin gp0,PIO1

PIO ASSEMBLE 1,".program toggle"
PIO assemble 1,".line 0"         'start line 0
PIO ASSEMBLE 1,"set pindirs,1"   'set GPIO to output
PIO ASSEMBLE 1,".wrap target"
PIO ASSEMBLE 1,"set pins,0"      'set low
PIO ASSEMBLE 1,"set pins,1"      'set high
PIO ASSEMBLE 1,".wrap"           'wrap back to wrap_target
PIO ASSEMBLE 1,".end program list"

'configure pio1 StateMachine 0
f0 = 63e6    '1MHz, change this to meet your need
'              a b c d e f g   'a,e=side set   c,g=OUT  b,f=set
p0 = Pio(PINCTRL 0,1,,,,GP0,)
e0 = Pio(EXECCTRL GP0,Pio(.wrap target),Pio(.wrap))

'write the configuration
PIO init machine 1,0,f0,p0,e0,,0        'SM0 start at address 0
PIO START 1,0

Do
 Pause 2000
 Print Pin(GP7)
Loop
>

Edit 2
FIN works ok when linked to a PWM pin.
Edited 2025-01-31 08:05 by phil99
PhenixRising
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Posted: 10:10pm 30 Jan 2025      

On the RP2350, GP0 supports the new-ish FFIN

What happens if you flip the roles?
phil99

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Posted: 10:30pm 30 Jan 2025      

Yes, it works with SETPIN GP1,FFIN
With CPU and PIO speed 378MHz FFIN reads 189MHz.

Edit. I should have read the manual!
Edited 2025-01-31 08:37 by phil99
PhenixRising
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Posted: 11:00pm 30 Jan 2025      

  phil99 said  Yes, it works with SETPIN GP1,FFIN


Ah, had it in my head that it was GP0 but I looked at my new board layout and sure-enough, I have it routed to GP1  
Bleep
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Posted: 02:27pm 03 Feb 2025      

Hi Harm,
Thanks very much for the PIO Frequency test program, I can confirm the PIO on my 2040  will run at full clock frequency at 420MHz.
so I have 'Option CPUCLOCK 420000' and 'f0 = 420E6' in the code, which give me this. :-)



Which is probably not too bad, all things considered.
Thanks again.
Regards, Kevin.
GAVI
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Posted: 03:03pm 03 Feb 2025      

as far as I know the 74HC14 cannot exceed 40 MhZ, but in practice even less.
Used as an output buffer for frequency of 100-200 MhZ it would not work at all.
Bleep
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Posted: 02:45pm 19 Feb 2025      

Hi Harm or Peter,
I've been experimenting with the PIO and Assembler.
Just because it looked like I could and I have a 4 channel scope, I wanted to modify your original code to now toggle 5 GPIO pins simultaniously, along with another 5 GPIO pins as Side Set, but out of phase.
I was originaly using the old assembler, but it looked as though there had been problems with compiling SideSet with that, so I've now swapped the the latest B11 and the new assembler.
This code was also to test the various drive strengths and speed settings, to see if there was a noticeable difference.
I have managed to get the 5 consecutive pins GPIO0 to GPIO4 all toggeling together, but have completely failed to get GPIO5 to GPIO9 to toggle using Side Set.
Any sugestions appreciated. :-)
Regards Kevin.
' Toggle multiple GPIO with set and out of phase with Side Set.
SetPin gp0,PIO1
SetPin gp1,PIO1
SetPin gp2,PIO1
SetPin gp3,PIO1
SetPin gp4,PIO1
SetPin gp5,PIO1
SetPin gp6,PIO1
SetPin gp7,PIO1
SetPin gp8,PIO1
SetPin gp9,PIO1

PIO ASSEMBLE 1
.program multi_toggle
.side set 5     ' pinsdir, &b11111   '5 side set pins
.line 0                ' start line 0
Set pindirs, &b11111   'set GPIO 0to4 to output"
.wrap target
Set pins,&b00000 side &b11111      'set low, side set high
Set pins,&b11111 side &b00000      'set high, side set low
.wrap                  'wrap back to wrap_target
.end program list

'configure pio1 StateMachine 0
f0 = 210e6    '100MHz, change this to meet your need
'              a b c d e f g   'a,e=side set   c,g=OUT  b,f=set
p0 = Pio(PINCTRL 5,5,,,GP5,GP0,)
e0 = Pio(EXECCTRL GP0,Pio(.wrap target),Pio(.wrap))

'write the configuration
PIO init machine 1,0,f0,p0,e0,,0        'SM0 start at address 0

PIO START 1,0

Timer =0
Dim Integer count=0
Print "Frequency =" f0/2000000"MHz"
Do
If Timer > 999 Then Timer =0:Inc count
Select Case count
Case 30
 Poke word &H4001c004,&H00
 Inc count
 Print "2mA, normal"
Case 40
 Poke word &H4001c004,&H01
 Inc count
 Print "2mA, Hi speed"
Case 50
 Poke word &H4001c004,&H10
 Inc count
 Print "4mA, normal"
Case 60
 Poke word &H4001c004,&H11
 Inc count
 Print "4mA, Hi speed"
Case 70
 Poke word &H4001c004,&H20
 Inc count
 Print "8mA, normal"
Case 80
 Poke word &H4001c004,&H21
 Inc count
 Print "8mA, Hi speed"
Case 90
 Poke word &H4001c004,&H30
 Inc count
 Print "12mA, normal"
Case 100
 Poke word &H4001c004,&H31
 Inc count
 Print "12mA, Hi speed"
Case 110
 Poke word &H4001c004,&H21
 Inc count
 Print "Standard, 8mA, Hi speed"
End Select
Loop
Volhout
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Posted: 06:50pm 19 Feb 2025      

Your proble. Is that gpio 5..9 are not set as output.

In the new assembler Peter has added a funtion that automatically sets pins defined in pinctrl, as output. Very handy in your case.

You have to look for details in the 6.00.02 beta thread. It is invoked by adding some additional ,1,1,1 to one of the pio commands.

You could also remove the set pindirs.

Volhout
Bleep
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Posted: 05:53pm 21 Feb 2025      

Hi Harm or Peter,
I've spent all day trying to get this working, I've read and Re-read the Beta 02 thread.
Just to be quite sure, this is on a RP2040, running latest B11.

If I remove the "Set pindirs, &b11111" I get no GPIO toggeling at all, so for the moment I'm leaving that in.

I've reduced the side set to only toggle 1 GPIO, just to make it simpler.

Reading the Beta 02 tread, it appears I need to set a bit at the end of the "Pio(EXECCTRL GP0,Pio(.wrap target),Pio(.wrap),0,1)" to enable Side set?, but this appears to do nothing?
If I add the opt command ".side set 1 opt" I no longer get a square wave out from the GPIO0 to GPIO5 being driven with "Set pins" I now get a pulse every fifth clock, so a 20MHz pulse, So I have no idea what that is actually doing? again I have removed it.

So I'm back to where I was, I have got all 5 "Set Pins" GPIO0 to GPIO5 toggeling, giving a reasonable square wave at 100MHZ, but I cannot get any life out of the side set pin or pins?

Any help appreciated.
Regards, Kevin.
' Toggle multiple 2040 GPIO with set and out of phase with Side Set.
SetPin gp0,PIO1
SetPin gp1,PIO1
SetPin gp2,PIO1
SetPin gp3,PIO1
SetPin gp4,PIO1
SetPin gp5,PIO1
SetPin gp6,PIO1
SetPin gp7,PIO1
SetPin gp8,PIO1
SetPin gp9,PIO1

PIO ASSEMBLE 1
.program multi_toggle
.side set 1     ' opt ' pinsdir, &b11111   '1 side set pins
.line 0                ' start line 0
Set pindirs, &b11111   'set GPIO 0to4 to output"
.wrap target
Set pins, &b00000 side 1      'set low, side set high
Set pins, &b11111 side 0      'set high, side set low
.wrap                  'wrap back to wrap_target
.end program list

'configure pio1 StateMachine 0
f0 = 210e6    '100MHz, change this to meet your need
'              a b c d e f g   'a,e=side set   c,g=OUT  b,f=set
p0 = Pio(PINCTRL 1,5,,,GP5,GP0,)
e0 = Pio(EXECCTRL GP0,Pio(.wrap target),Pio(.wrap),0,1)

'write the configuration
PIO init machine 1,0,f0,p0,e0,,0        'SM0 start at address 0

PIO START 1,0

Timer =0
Dim Integer count=0
Print "Frequency =" f0/2000000"MHz"
Do
If Timer > 999 Then Timer =0:Inc count
Select Case count
Case 30
 Poke word &H4001c004,&H00
 Inc count
 Print "2mA, normal"
Case 40
 Poke word &H4001c004,&H01
 Inc count
 Print "2mA, Hi speed"
Case 50
 Poke word &H4001c004,&H10
 Inc count
 Print "4mA, normal"
Case 60
 Poke word &H4001c004,&H11
 Inc count
 Print "4mA, Hi speed"
Case 70
 Poke word &H4001c004,&H20
 Inc count
 Print "8mA, normal"
Case 80
 Poke word &H4001c004,&H21
 Inc count
 Print "8mA, Hi speed"
Case 90
 Poke word &H4001c004,&H30
 Inc count
 Print "12mA, normal"
Case 100
 Poke word &H4001c004,&H31
 Inc count
 Print "12mA, Hi speed"
Case 110
 Poke word &H4001c004,&H21
 Inc count
 Print "Standard, 8mA, Hi speed"
End Select
Loop

Edited 2025-02-22 03:55 by Bleep
matherp
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Posted: 06:11pm 21 Feb 2025      

opt uses one of the five bits available to delay and/or side_set. You can't have 5 side_set and opt. Try with just 4
Bleep
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Posted: 07:10pm 21 Feb 2025      

I was only using 1 side set bit at the time, I seem to remember if I tried nto use 5 and put the "opt" in it would not compile with an error. I don't want to use "opt", it was just an experiment.
Edited 2025-02-22 05:11 by Bleep
matherp
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Posted: 07:28pm 21 Feb 2025      

PIO INIT MACHINE PIO%,
stateMACHINE%, clockspeed
[,pinctrl] [,execctrl] [,shiftctrl]
[,startinstruction] [,sideout [,setout] [,outout]

sideout, setout, and outout can be set to 0 (default) or 1 to specify if pins defined in pinctrl should be INITialised as inputs (0) or outputs (1)
Bleep
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Posted: 08:42pm 21 Feb 2025      

Ah ok thanks Peter, I'll give that a try and report back.