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homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 07:03pm 12 Aug 2024

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Hi guys,

I'm going to try the PIOs again. First I want to receive a MIDI signal (serial 8N1 at 31250 baud). This works fine with the UARTs. But now I want to learn how to use the PIOs.
I have chosen the GP15 as the input pin.
I also used this source for the PIO programmer: https://github.com/raspberrypi/pico-examples/blob/master/pio/uart_rx/uart_rx.pio

I have consulted the manual "Appendix F - The PIO Programming Package" and the link there.
But I have problems to understand

the >option list
WebMite MMBasic Version 5.08.00
OPTION COLOURCODE ON

Here is my Basic attempt which unfortunately fails:

'Only PIO 0 is available on the WebMite
'as PIO1 is used by the WIFI interface

'disconnect ARM from GP15
' SETPIN GP15,PIO0

'PIO program
PIO ASSEMBLE 0,".program uart_rx" 'a program needs a Name
PIO ASSEMBLE 0,".wrap target"
PIO ASSEMBLE 0,"start:"
PIO ASSEMBLE 0,"wait 0 pin 0"
PIO ASSEMBLE 0,"set x, 7 [10]"
PIO ASSEMBLE 0,"bitloop:"
PIO ASSEMBLE 0,"in pins, 1"
PIO ASSEMBLE 0,"jmp x-- bitloop [6]"
PIO ASSEMBLE 0,"jmp pin good_stop"
PIO ASSEMBLE 0,"irq 4 rel"
PIO ASSEMBLE 0,"wait 1 pin 0"
PIO ASSEMBLE 0,"jmp start"
PIO ASSEMBLE 0,"good_stop:"
PIO ASSEMBLE 0,"push"
PIO ASSEMBLE 0,".wrap"
PIO ASSEMBLE 0,".end program list"

Print "CPUspeed", MM.Info(CPUSPEED)

Pause 1000

'configure pio0
p=Pio(PINCTRL 0,0,,gp15,,,) 'gp15 in
f=15625 'Hz for 31250 baud, MIDI 8n1 > 31250/2 = 15625 Hz ?!
s=Pio(shiftctrl 0,0,0,0,0,0) 'shift in from LSB for IN
e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap) )

'write the configuration
PIO init machine 0,0,f,p,e,s,0

'start the pio0 code
PIO start 0,0

'Check the the read data in MMBasic and print
Dim d%,b%
Do
PIO read 0,0,1,d%
b%=d% Xor &hFF
If b%>0 Then Print Bin$(b%), Hex$(b%)
'Pause 200
Loop
End

Who can help me and give me the right hint?

PhenixRising
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Joined: 07/11/2023
Location: United Kingdom
Posts: 857

Posted: 09:51pm 12 Aug 2024

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Cool 😎
We sorely need MIDI stuff

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 4222

Posted: 06:04am 13 Aug 2024

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Hi Homa,

When the uart should run 31250 baud, the PIO clock must be a multiple of that. I have no access to pico atm. Cannot help you short time. But try f=2*31250, or f=3*31250.

Volhout

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homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 05:53pm 13 Aug 2024

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Hi Volhout,

Thanks for your tip, according to my research it should actually be baud = Hz. But I also tried f *2 or f *3. Unfortunately without success.
First I added the interrupt to separate the bytes. But the result is not what I expected :-(

> run
0: 2020
1: EA27
2: 4001
3: 0642
4: 00C8
5: C014
6: 20A0
7: 0000
8: 8000
CPUspeed 133000000
11100000 E0
10000000 80
>

I actually expect something like this (when I press a midi keyboad button) as it comes via UART and is correct:

10010000 90
110000 30
100000 20
110000 30
0 0

Current programme code:

'PIO program
PIO ASSEMBLE 0,".program uart_rx" 'a program needs a Name
PIO ASSEMBLE 0,".wrap target"
PIO ASSEMBLE 0,"start:"
PIO ASSEMBLE 0,"wait 0 pin 0"
PIO ASSEMBLE 0,"set x, 7 [10]"
PIO ASSEMBLE 0,"bitloop:"
PIO ASSEMBLE 0,"in pins, 1"
PIO ASSEMBLE 0,"jmp x-- bitloop [6]"
PIO ASSEMBLE 0,"jmp pin good_stop"
PIO ASSEMBLE 0,"irq 4 rel"
PIO ASSEMBLE 0,"wait 1 pin 0"
PIO ASSEMBLE 0,"jmp start"
PIO ASSEMBLE 0,"good_stop:"
PIO ASSEMBLE 0,"push"
PIO ASSEMBLE 0,".wrap"
PIO ASSEMBLE 0,".end program list"

Print "CPUspeed", MM.Info(CPUSPEED)

Pause 100

Dim d%,b%

'configure pio0
p=Pio(PINCTRL 0,0,,gp15,,,) 'gp15 in
f=31250 '? Hz for 31250 baud, MIDI 8n1 ?!?
s=Pio(shiftctrl 0,0,0,0,0,0) 'shift in from LSB for IN
e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap) )

'write the configuration
PIO init machine 0,0,f,p,e,s,0

PIO INTERRUPT 0,0,myPioRX,0

'start the pio0 code
PIO start 0,0

' MAIN
Do
' PIO read 0,0,1,d%
' b%=d% Xor &hFF
' If b%>0 Then Print Bin$(b%), Hex$(b%)
' Pause 20
Loop
End

Sub myPioRX
' PIO stop 0,0
' PIO init machine 0,0,f,p,e,s,0

PIO read 0,0,1,d%
b%=d% Xor &hFF
Print Bin$(b%), Hex$(b%)

' PIO start 0,0
End Sub

Matthias
Edited 2024-08-14 03:54 by homa

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 9109

Posted: 05:59pm 13 Aug 2024

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For a bitbanged serial the clock rate is typically 2x baud rate
Wait for the start bit
Wait 1.5x bit time

repeat x8
sample input
wait bit time
loop

If I read your code correctly you are sampling as the bit is changing

homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 08:04pm 13 Aug 2024

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Hello Peter, hello Volhout,

I did it. Now I understand the PIO example code more and more.
I still have some questions!
The PIO example says the following:

; Autopush must be enabled, with a threshold of 8.
// Shift to right, autopush enabled
sm_config_set_in_shift(&c, true, true, 8);

sm_config_set_fifo_join(&c, PIO_FIFO_JOIN_RX);

// SM transmits 1 bit per 8 execution cycles.
float div = (float)clock_get_hz(clk_sys) / (8 * baud);
sm_config_set_clkdiv(&c, div);

So I reduced the PIO code to the simpler example. I adjusted the frequency to the baud rate and used the MMBasic command
PIO(SHIFTCTRL a,b,c,d,e,f,g,h), c/ autopush
is enabled. However, a 32-bit value is returned. Is it possible to enable 8-bit autopush as in the notes? And if so, how?

I have done this by adding
PIO ASSEMBLE 0, "push"
which solved the problem.

I also had the shift direction wrong.
Now:
s=Pio(shiftctrl 0,0,0,0,1,0) 'shift in from MSB for IN

To make the 32-Bit value correct, I added the "value>>24" to the output in MMBasic.

Thanks for your suggestions!

> run
0: 2020
1: EA27
2: 4001
3: 0642
4: 8000
CPUspeed 133000000
10010000 90 144
110000 30 48
1010100 54 84
110000 30 48
0 0 0

'PIO program
PIO ASSEMBLE 0,".program uart_rx"
PIO ASSEMBLE 0,".wrap target"
PIO ASSEMBLE 0,"wait 0 pin 0"
PIO ASSEMBLE 0,"set x, 7 [10]"
PIO ASSEMBLE 0,"bitloop:"
PIO ASSEMBLE 0,"in pins, 1"
PIO ASSEMBLE 0,"jmp x-- bitloop [6]"
PIO ASSEMBLE 0,"push"
PIO ASSEMBLE 0,".wrap"
PIO ASSEMBLE 0,".end program list"

Print "CPUspeed", MM.Info(CPUSPEED)

Pause 100
Dim d%,b%

'configure pio0
p=Pio(PINCTRL 0,0,,gp15,,,) 'gp15 in
f=31250*8 'Hz for 31250 baud, MIDI 8n1 = *8 for the PIO-Code!
s=Pio(shiftctrl 0,0,0,0,1,0) 'shift in from MSB for IN
e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap) )

'write the configuration
PIO init machine 0,0,f,p,e,s,0
PIO INTERRUPT 0,0,myPioRX,0
'start the pio0 code
PIO start 0,0

'MAIN
Do
'nothing
Loop
End

Sub myPioRX
PIO read 0,0,1,d%
b%=d%>>24
Print Bin$(b%), Hex$(b%), b%
End Sub

Matthias

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 4222

Posted: 05:47am 14 Aug 2024

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Goog work Matthias, you are understanding PIO well

Thanks Peter, for helping out

Volhout

PicomiteVGA PETSCII ROBOTS

homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 06:57pm 17 Aug 2024

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Unfortunately, I haven't quite understood it yet :-(
Now I want to try the other direction (send) and I fail ...
It looks like the OUT does not write from the OSR to the PIN.
Can anyone tell me my mistake?

Matthias

' pio out TEST
'--------------------------------------------------
'Only PIO 0 is available on the WebMite
'as PIO1 is used by the WIFI interface
'
'disconnect ARM from GP14
SetPin GP14,pio0
Dim d%,b%,o%
'
PIO ASSEMBLE 0,".program uart_tx"
PIO ASSEMBLE 0,".side_set 1"
PIO ASSEMBLE 0,"set pindirs, 1"
PIO ASSEMBLE 0,".wrap target"
PIO ASSEMBLE 0,"pull side 1 [7]"
PIO ASSEMBLE 0,"set x, 7 side 0 [7]"
PIO ASSEMBLE 0,"bitloop:"
PIO ASSEMBLE 0,"out pins, 1 "
PIO ASSEMBLE 0,"jmp x-- bitloop [6]"
PIO ASSEMBLE 0,".wrap"
PIO ASSEMBLE 0,".end program list"
'configure pio0 StateMachine 1
f=31250*8
' a b c d e f g a,e=side set c,g=OUT
p=Pio(PINCTRL 1,1,1,gp15,gp14,gp14,gp14)
e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap) )
' 7 .
s=Pio(shiftctrl 0,7,0,0,1,1)
'write the configuration
PIO init machine 0,0,f,p,e,s,0
'start the pio0 code state machine 0
PIO start 0,0
'MAIN
Do
'nothing
Pause 500
o%=&haa
Print Bin$(o%)
'Print "Status1:", Pio(FLEVEL 0 ,0 , tx)
PIO write 0,0,1,o%
Print "..."
Loop
End

homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 05:19pm 20 Aug 2024

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@Volhout: please check your PM, thx.

Matthias

Volhout
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Joined: 05/03/2018
Location: Netherlands
Posts: 4222

Posted: 07:49am 24 Aug 2024

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Hi Matthias,

When using SIDE SET, a field in each instruction is reserved for SIDE SET.
But there are many instructions where SIDE SET is not to be executed.
There is a configuration in the EXECCTRL register that only activates SIDE SET when it is actively programmed in the assembler.

In your program, change:

e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap) )

into

e=Pio(execctrl gp15,Pio(.wrap target),Pio(.wrap),0,1 ) 'side set only when defined

Then, it works....

So in essence, your program worked, but on each instruction (also the OUT) the hidden SIDE SET re-programmed the GPIO pin to 0.

Volhout

P.s. you may have to change the PULL into PULL BLOCK so you only send data when there is new data in the fifo.
Edited 2024-08-24 21:10 by Volhout

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homa

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Joined: 05/11/2021
Location: Germany
Posts: 351

Posted: 11:37am 25 Aug 2024

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You are a genius for PIO :-)
Peter was not wrong to refer to you.

But why doesn't it say so in the manual or do I have tomatoes on my eyes? ... ye...no ...

I found this: “[,side_pindir][,side_en]” BUT without any explanation. @geoffg: “Please add this to the manual. Especially in the appendix there is no mention of this yet!”

Matthias

Volhout
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Location: Netherlands
Posts: 4222

Posted: 05:47pm 25 Aug 2024

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Actually, this is an omission from my side. When I wrote the text for this chapter, the 2 fields where not defined yet. At some moment in time these fields where added by Peter, and the manual was not updated.

Volhout

PicomiteVGA PETSCII ROBOTS

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