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====== PIO (dis)assembler v2 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 =====
Note that; this is version-2 of the PIO (dis)assembler.\\
This version is more flexible and is prepared for more than two PIO's.
The sample code assumes a 32-bit machine with 32-bit compile operations.
It is also assumed 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:
+TO ( n "name" -- ) - Add n to the contents of the value "name"
VOCABULARY ( "name" -- ) - Define a named wordlist
==== The structure of PIO opcodes ====
Pink = Opcode field
Yellow = Delay and/or side set field
Green = Destination field
Blue = Data field
{{pfw:set_jpg.jpg}}
==== All PIO instructions ====
✦ 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 three one> two> three>
✦ 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> =pio
sm-on exec freq clock-div sync
restart
✦ PIO disassembler & state machine data
psee psee0 psee1 .fifo .sm
==== Usage example ====
An extra RS232 output driver in only 5 instructions!
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}
==== UART control code ====
: PEMIT ( ch -- ) begin 0 tx-depth 3 < until 0 >txf ;
: PTYPE ( a u -- ) 0 ?do count pemit loop drop ;
: ABC ( -- ) s" ABC " ptype ;
{{pfw:pio_uart.jpg}}
Alternative Implementations
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