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====== PIO (dis)assembler for RP2040 ======

===== The idea: =====

''PIO'' stand for **P**rogrammable **I**nput **O**utput. These are programmable state machines
with a small shared program memory. Programs are built with only eight instructions.  The
behavior of those instructions can be modified with registers.

We define a (standalone) ''PIO'' forth style (dis)assembler for the RP2040. It can be used for writing direct executable programs and exportable HEX programs. These HEX programs can be used in conjunction with the mini-PIO control program.

{{ :pfw:one_pio_sm.jpg?500 |One PIO state machine}}
===== Implementation =====

The example code asumes a 32-bit machine that has 32-bit compile actions. 
It is also asumed that the code runs in RAM as noForth T on the RP2040 does.
All PIO fuctionality can be used, and a PIO-module ''%%EXPORT%%'' function is provided.
The PIO-assembler is (de)activated by the words ''%%{PIO%%'' and ''%%PIO}%%''. 
Missing words in Generic Forth are:

<code forth>
+TO         ( n "name" -- )     - Add n to the contents of the value "name"
VOCABULARY  ( "name" -- )       - Define a named wordlist
</code>

==== The structure of PIO opcodes ====

<code>
Pink   = Opcode field
Yellow = Delay and/or side set field
Green  = Destination field
Blue   = Data field
</code>
{{pfw:set_jpg.jpg}}
==== All PIO instructions ====

<code forth>

✦ PIO opcodes
    in,         out,        push,       pull,       mov,        wait,
    irq,        set,        nop,        pio,        
    
✦  Optional arguments for each opcode
    []         side
    
✦ Conditionals
    x0<>?       x--?        y0<>?       y--?        x=y?        pin?
    osre?

✦ Control structures
    if,         else,       then,      begin,      while,      repeat,
    again,      until,
    
✦ Labels
    one         two         one>        two>

✦ PIO directives
    clean-pio   =pio        sm          sync        restart
    =org        =set-pins   =out-pins   =side-pins  opt
    =in-pin     =jmp-pin    =inputs     =strength   side-pindirs
    wrap-target wrap        =steal      =autopush   =autopull
    =in-dir     =out-dir    clone       =exec       =clock-div
    =freq       export

✦ PIO external tools (mini-PIO.f)
    tx-depth    rx-depth    >txf        rxf>        set-pio
    sm-on       exec        freq        clock-div   sync
    restart

✦ PIO disassembler & state machine data
    mpsee       psee        .fifo       .sm

</code>

==== Usage example ====

An extra RS232 output driver in only 5 instructions!

<code>
decimal
: =BAUD ( b -- )    8 *  =freq ; \ Set baudrate for UART

clean-pio                   \ Empty code space, start at zero
0 0 {pio                    \ Use state machine-0 on PIO-0
    115200 =baud            \ 115k2
    26 1 =side-pins  opt    \ GPIO 26 for optional SIDE
    26 1 =out-pins          \ GPIO 26 for OUT & SET
    26 1 =set-pins
    1 pindirs set,              \ Pin is output!
    wrap-target
        7 []  1 side  pull,     \ Stop bit, get data byte
        7 []  0 side 7 x set,   \ Start bit
        begin,
            1 pins out,         \ Shift 8 bits out
        6 []  x--? until,       \ Until 8 bits are done
    wrap
    0 =exec                 \ Start SM-0 code at address 0
pio}
</code>

==== UART control code ====

<code>
: PEMIT ( ch -- )   begin  0 tx-depth  3 < until  0 >txf ;
: PTYPE ( a u -- )  0 ?do  count pemit  loop  drop ;
: ABC   ( -- )      s" ABC " ptype ;
</code>

{{pfw:pio_uart.jpg}}

<code></code>
| File name | Purpose | in Dropbox (external link) |
| [[https://www.dropbox.com/s/edo8rk339awuerz/PIO%20assembler%20docs.pdf?dl=1|PIO-assembler docs.pdf]] | Documentation | [[https://www.dropbox.com/s/edo8rk339awuerz/PIO%20assembler%20docs.pdf?dl=0|PIO-assembler documentation]] |
| [[https://www.dropbox.com/s/l39qwo088l6i8sm/PIO%20assembler%20overview.pdf?dl=1|PIO assembler overview.pdf]] | Documentation | [[https://www.dropbox.com/s/l39qwo088l6i8sm/PIO%20assembler%20overview.pdf?dl=0|PIO-assembler overview]] |
| [[https://www.dropbox.com/s/65e148ce9lckt0j/PIO-assembler%20uni.f?dl=0| PIO-assembler uni.f]] | PIO-assembler | [[https://www.dropbox.com/s/boi1znyduiegdlu/PIO-assembler.f?dl=0|noForth PIO assembler]] |
| [[https://www.dropbox.com/s/3kvf637vuy4ymhd/PIO-disassembler%20uni.f?dl=0| PIO-disassembler uni.f]] | PIO-disassembler | [[https://www.dropbox.com/s/rhilv9gr6b6vsx9/PIO-disassembler.f?dl=0|noForth PIO disassembler]] |
| [[https://www.dropbox.com/s/gzfccww59e8ms6z/mini-PIO%20uni.f?dl=0|Mini-PIO uni.f]] | mini-PIO tool set | [[https://www.dropbox.com/s/lw638dy1udsz83h/mini-PIO.f?dl=0|noForth minimal PIO controller]] |

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==== Contributions ====

<html><h2 style="background-color:yellow">Alternative Implementations</h2></html>


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