Initial Release

pio/squarewave/CMakeLists.txt

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+add_executable(pio_squarewave)
+
+pico_generate_pio_header(pio_squarewave ${CMAKE_CURRENT_LIST_DIR}/squarewave.pio)
+pico_generate_pio_header(pio_squarewave ${CMAKE_CURRENT_LIST_DIR}/squarewave_wrap.pio)
+pico_generate_pio_header(pio_squarewave ${CMAKE_CURRENT_LIST_DIR}/squarewave_fast.pio)
+
+target_sources(pio_squarewave PRIVATE squarewave.c)
+
+target_link_libraries(pio_squarewave PRIVATE pico_stdlib hardware_pio)
+pico_add_extra_outputs(pio_squarewave)
+
+# add url via pico_set_program_url
+example_auto_set_url(pio_squarewave)
+
+# generate .hex file and .pio.h file for the RP2040 datasheet (to make sure
+# the datasheet always shows the output of the latest pioasm version)
+add_custom_target(pio_squarewave_datasheet DEPENDS
+		Pioasm
+		${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.hex
+		${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.pio.h
+		${CMAKE_CURRENT_LIST_DIR}/generated/squarewave_wrap.pio.h
+		)
+add_custom_command(OUTPUT ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.hex
+        DEPENDS ${CMAKE_CURRENT_LIST_DIR}/squarewave.pio
+        COMMAND Pioasm -o hex ${CMAKE_CURRENT_LIST_DIR}/squarewave.pio ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.hex
+        )
+add_custom_command(OUTPUT ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.pio.h
+        DEPENDS ${CMAKE_CURRENT_LIST_DIR}/squarewave.pio
+        COMMAND Pioasm ${CMAKE_CURRENT_LIST_DIR}/squarewave.pio ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave.pio.h
+        )
+add_custom_command(OUTPUT ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave_wrap.pio.h
+        DEPENDS ${CMAKE_CURRENT_LIST_DIR}/squarewave_wrap.pio
+        COMMAND Pioasm ${CMAKE_CURRENT_LIST_DIR}/squarewave_wrap.pio ${CMAKE_CURRENT_LIST_DIR}/generated/squarewave_wrap.pio.h
+        )
+add_dependencies(pio_squarewave pio_squarewave_datasheet)

pio/squarewave/generated/squarewave.hex

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+e081
+e101
+e000
+0001

pio/squarewave/generated/squarewave.pio.h

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+// -------------------------------------------------- //
+// This file is autogenerated by pioasm; do not edit! //
+// -------------------------------------------------- //
+
+#if !PICO_NO_HARDWARE
+#include "hardware/pio.h"
+#endif
+
+// ---------- //
+// squarewave //
+// ---------- //
+
+#define squarewave_wrap_target 0
+#define squarewave_wrap 3
+
+static const uint16_t squarewave_program_instructions[] = {
+            //     .wrap_target
+    0xe081, //  0: set    pindirs, 1                 
+    0xe101, //  1: set    pins, 1                [1] 
+    0xe000, //  2: set    pins, 0                    
+    0x0001, //  3: jmp    1                          
+            //     .wrap
+};
+
+#if !PICO_NO_HARDWARE
+static const struct pio_program squarewave_program = {
+    .instructions = squarewave_program_instructions,
+    .length = 4,
+    .origin = -1,
+};
+
+static inline pio_sm_config squarewave_program_get_default_config(uint offset) {
+    pio_sm_config c = pio_get_default_sm_config();
+    sm_config_set_wrap(&c, offset + squarewave_wrap_target, offset + squarewave_wrap);
+    return c;
+}
+#endif
+

pio/squarewave/generated/squarewave_wrap.pio.h

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+// -------------------------------------------------- //
+// This file is autogenerated by pioasm; do not edit! //
+// -------------------------------------------------- //
+
+#if !PICO_NO_HARDWARE
+#include "hardware/pio.h"
+#endif
+
+// --------------- //
+// squarewave_wrap //
+// --------------- //
+
+#define squarewave_wrap_wrap_target 1
+#define squarewave_wrap_wrap 2
+
+static const uint16_t squarewave_wrap_program_instructions[] = {
+    0xe081, //  0: set    pindirs, 1                 
+            //     .wrap_target
+    0xe101, //  1: set    pins, 1                [1] 
+    0xe100, //  2: set    pins, 0                [1] 
+            //     .wrap
+};
+
+#if !PICO_NO_HARDWARE
+static const struct pio_program squarewave_wrap_program = {
+    .instructions = squarewave_wrap_program_instructions,
+    .length = 3,
+    .origin = -1,
+};
+
+static inline pio_sm_config squarewave_wrap_program_get_default_config(uint offset) {
+    pio_sm_config c = pio_get_default_sm_config();
+    sm_config_set_wrap(&c, offset + squarewave_wrap_wrap_target, offset + squarewave_wrap_wrap);
+    return c;
+}
+#endif
+

pio/squarewave/squarewave.c

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+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// Output a 12.5 MHz square wave (if system clock frequency is 125 MHz).
+//
+// Note this program is accessing the PIO registers directly, for illustrative
+// purposes. We pull this program into the datasheet so we can talk a little
+// about PIO's hardware register interface. The `hardware_pio` SDK library
+// provides simpler or better interfaces for all of these operations.
+//
+// _*This is not best practice! I don't want to see you copy/pasting this*_
+//
+// For a minimal example of loading and running a program using the SDK
+// functions (which is what you generally want to do) have a look at
+// `hello_pio` instead. That example is also the subject of a tutorial in the
+// SDK book, which walks you through building your first PIO program.
+
+#include "pico/stdlib.h"
+#include "hardware/pio.h"
+
+// Our assembled program:
+#include "squarewave.pio.h"
+
+int main() {
+    // Pick one PIO instance arbitrarily. We're also arbitrarily picking state
+    // machine 0 on this PIO instance (the state machines are numbered 0 to 3
+    // inclusive).
+    PIO pio = pio0;
+
+    /// \tag::load_program[]
+    // Load the assembled program directly into the PIO's instruction memory.
+    // Each PIO instance has a 32-slot instruction memory, which all 4 state
+    // machines can see. The system has write-only access.
+    for (int i = 0; i < count_of(squarewave_program_instructions); ++i)
+        pio->instr_mem[i] = squarewave_program_instructions[i];
+    /// \end::load_program[]
+
+    /// \tag::clock_divider[]
+    // Configure state machine 0 to run at sysclk/2.5. The state machines can
+    // run as fast as one instruction per clock cycle, but we can scale their
+    // speed down uniformly to meet some precise frequency target, e.g. for a
+    // UART baud rate. This register has 16 integer divisor bits and 8
+    // fractional divisor bits.
+    pio->sm[0].clkdiv = (uint32_t) (2.5f * (1 << 16));
+    /// \end::clock_divider[]
+
+    /// \tag::setup_pins[]
+    // There are five pin mapping groups (out, in, set, side-set, jmp pin)
+    // which are used by different instructions or in different circumstances.
+    // Here we're just using SET instructions. Configure state machine 0 SETs
+    // to affect GPIO 0 only; then configure GPIO0 to be controlled by PIO0,
+    // as opposed to e.g. the processors.
+    pio->sm[0].pinctrl =
+            (1 << PIO_SM0_PINCTRL_SET_COUNT_LSB) |
+            (0 << PIO_SM0_PINCTRL_SET_BASE_LSB);
+    gpio_set_function(0, GPIO_FUNC_PIO0);
+    /// \end::setup_pins[]
+
+    /// \tag::start_sm[]
+    // Set the state machine running. The PIO CTRL register is global within a
+    // PIO instance, so you can start/stop multiple state machines
+    // simultaneously. We're using the register's hardware atomic set alias to
+    // make one bit high without doing a read-modify-write on the register.
+    hw_set_bits(&pio->ctrl, 1 << (PIO_CTRL_SM_ENABLE_LSB + 0));
+    /// \end::start_sm[]
+
+    return 0;
+
+}

pio/squarewave/squarewave.pio

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+;
+; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+;
+; SPDX-License-Identifier: BSD-3-Clause
+;
+
+.program squarewave
+    set pindirs, 1   ; Set pin to output
+again:
+    set pins, 1 [1]  ; Drive pin high and then delay for one cycle
+    set pins, 0      ; Drive pin low
+    jmp again        ; Set PC to label `again`
+

pio/squarewave/squarewave_fast.pio

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+;
+; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+;
+; SPDX-License-Identifier: BSD-3-Clause
+;
+
+; Note that if you modify squarewave.c to include this program, you'll also
+; need to set the wrap registers yourself. This would be handled for you by
+; squarewave_program_get_default_config().
+
+
+.program squarewave_fast
+; Like squarewave_wrap, but remove the delay cycles so we can run twice as fast.
+    set pindirs, 1   ; Set pin to output
+.wrap_target
+	set pins, 1      ; Drive pin high
+	set pins, 0      ; Drive pin low
+.wrap
+

pio/squarewave/squarewave_wrap.pio

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+;
+; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+;
+; SPDX-License-Identifier: BSD-3-Clause
+;
+
+; Note that if you modify squarewave.c to include this program, you'll also
+; need to set the wrap registers yourself. This would be handled for you by
+; squarewave_program_get_default_config().
+
+.program squarewave_wrap
+; Like squarewave, but use the state machine's .wrap hardware instead of an
+; explicit jmp. This is a free (0-cycle) unconditional jump.
+
+    set pindirs, 1   ; Set pin to output
+.wrap_target
+	set pins, 1 [1]  ; Drive pin high and then delay for one cycle
+	set pins, 0 [1]  ; Drive pin low and then delay for one cycle
+.wrap