mimxrt/machine_bitstream: Add bitstream function to machine module.

Following the code example for ESP32 of Jim Mussard.

As a side effect:
- mp_hal_ticks_cpu() was implemented,
- mp_hal_get_cpu_freq() and mp_hal_ticks_cpu_init() were added and used.
- mp_hal_pin_high() and mp_hal_pin_low() were changed for symmetry

5 files changed, 92 insertions, 4 deletions

diff --git a/ports/mimxrt/Makefile b/ports/mimxrt/Makefile
index 58fbe2df3..8b1bb2bfa 100644
--- a/ports/mimxrt/Makefile
+++ b/ports/mimxrt/Makefile
@@ -152,6 +152,7 @@ SRC_C += \
 	fatfs_port.c \
 	led.c \
 	machine_adc.c \
+	machine_bitstream.c \
 	machine_i2c.c \
 	machine_led.c \
 	machine_pin.c \
diff --git a/ports/mimxrt/machine_bitstream.c b/ports/mimxrt/machine_bitstream.c
new file mode 100644
index 000000000..c6ff469ea
--- /dev/null
+++ b/ports/mimxrt/machine_bitstream.c
@@ -0,0 +1,73 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021 Jim Mussared
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+// This is a translation of the cycle counter implementation in ports/stm32/machine_bitstream.c.
+
+#include "py/mpconfig.h"
+#include "py/mphal.h"
+
+#if MICROPY_PY_MACHINE_BITSTREAM
+
+#define NS_TICKS_OVERHEAD (6)
+
+void machine_bitstream_high_low(mp_hal_pin_obj_t pin, uint32_t *timing_ns, const uint8_t *buf, size_t len) __attribute__((section(".ram_functions")));
+void machine_bitstream_high_low(mp_hal_pin_obj_t pin, uint32_t *timing_ns, const uint8_t *buf, size_t len) {
+    uint32_t fcpu_mhz = mp_hal_get_cpu_freq() / 1000000;
+    // Convert ns to us ticks [high_time_0, period_0, high_time_1, period_1].
+    for (size_t i = 0; i < 4; ++i) {
+        timing_ns[i] = fcpu_mhz * timing_ns[i] / 1000;
+        if (timing_ns[i] > NS_TICKS_OVERHEAD) {
+            timing_ns[i] -= NS_TICKS_OVERHEAD;
+        }
+        if (i % 2 == 1) {
+            // Convert low_time to period (i.e. add high_time).
+            timing_ns[i] += timing_ns[i - 1];
+        }
+    }
+    // Enable the CPU cycle counter, which is not always enabled.
+    mp_hal_ticks_cpu_init();
+
+    uint32_t irq_state = mp_hal_quiet_timing_enter();
+
+    for (size_t i = 0; i < len; ++i) {
+        uint8_t b = buf[i];
+        for (size_t j = 0; j < 8; ++j) {
+            uint32_t start_ticks = mp_hal_ticks_cpu();
+            mp_hal_pin_high(pin);
+            uint32_t *t = &timing_ns[b >> 6 & 2];
+            while ((mp_hal_ticks_cpu() - start_ticks) < t[0]) {
+            }
+            mp_hal_pin_low(pin);
+            b <<= 1;
+            while ((mp_hal_ticks_cpu() - start_ticks) < t[1]) {
+            }
+        }
+    }
+
+    mp_hal_quiet_timing_exit(irq_state);
+}
+
+#endif // MICROPY_PY_MACHINE_BITSTREAM
diff --git a/ports/mimxrt/modmachine.c b/ports/mimxrt/modmachine.c
index a98d09bd0..2e8753df1 100644
--- a/ports/mimxrt/modmachine.c
+++ b/ports/mimxrt/modmachine.c
@@ -26,6 +26,7 @@
  */
 
 #include "py/runtime.h"
+#include "extmod/machine_bitstream.h"
 #include "extmod/machine_mem.h"
 #include "extmod/machine_i2c.h"
 #include "extmod/machine_pulse.h"
@@ -45,7 +46,7 @@ STATIC mp_obj_t machine_reset(void) {
 MP_DEFINE_CONST_FUN_OBJ_0(machine_reset_obj, machine_reset);
 
 STATIC mp_obj_t machine_freq(void) {
-    return MP_OBJ_NEW_SMALL_INT(CLOCK_GetFreq(kCLOCK_CpuClk));
+    return MP_OBJ_NEW_SMALL_INT(mp_hal_get_cpu_freq());
 }
 MP_DEFINE_CONST_FUN_OBJ_0(machine_freq_obj, machine_freq);
 
@@ -97,6 +98,9 @@ STATIC const mp_rom_map_elem_t machine_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_disable_irq),         MP_ROM_PTR(&machine_disable_irq_obj) },
     { MP_ROM_QSTR(MP_QSTR_enable_irq),          MP_ROM_PTR(&machine_enable_irq_obj) },
 
+    #if MICROPY_PY_MACHINE_BITSTREAM
+    { MP_ROM_QSTR(MP_QSTR_bitstream),           MP_ROM_PTR(&machine_bitstream_obj) },
+    #endif
     { MP_ROM_QSTR(MP_QSTR_time_pulse_us),       MP_ROM_PTR(&machine_time_pulse_us_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(machine_module_globals, machine_module_globals_table);
diff --git a/ports/mimxrt/mpconfigport.h b/ports/mimxrt/mpconfigport.h
index 9775b29ef..0fe6cd129 100644
--- a/ports/mimxrt/mpconfigport.h
+++ b/ports/mimxrt/mpconfigport.h
@@ -124,6 +124,7 @@ uint32_t trng_random_u32(void);
 #define MICROPY_PY_USELECT                  (1)
 #define MICROPY_PY_MACHINE                  (1)
 #define MICROPY_PY_MACHINE_PIN_MAKE_NEW     mp_pin_make_new
+#define MICROPY_PY_MACHINE_BITSTREAM        (1)
 #define MICROPY_PY_MACHINE_PULSE            (1)
 #define MICROPY_PY_MACHINE_I2C              (1)
 #define MICROPY_PY_MACHINE_SOFTI2C          (1)
diff --git a/ports/mimxrt/mphalport.h b/ports/mimxrt/mphalport.h
index 94f43001d..3f0ae51bb 100644
--- a/ports/mimxrt/mphalport.h
+++ b/ports/mimxrt/mphalport.h
@@ -30,6 +30,7 @@
 #include <stdint.h>
 #include "ticks.h"
 #include "pin.h"
+#include "fsl_clock.h"
 
 #define MP_HAL_PIN_FMT                  "%q"
 
@@ -39,8 +40,8 @@
 #define mp_hal_pin_input(p) machine_pin_set_mode(p, PIN_MODE_IN);
 #define mp_hal_pin_output(p) machine_pin_set_mode(p, PIN_MODE_OUT);
 #define mp_hal_pin_open_drain(p) machine_pin_set_mode(p, PIN_MODE_OPEN_DRAIN);
-#define mp_hal_pin_high(p) (GPIO_PinWrite(p->gpio, p->pin, 1U))
-#define mp_hal_pin_low(p) (GPIO_PinWrite(p->gpio, p->pin, 0U))
+#define mp_hal_pin_high(p) (p->gpio->DR_SET = 1 << p->pin)
+#define mp_hal_pin_low(p) (p->gpio->DR_CLEAR = 1 << p->pin)
 #define mp_hal_pin_write(p, value) (GPIO_PinWrite(p->gpio, p->pin, value))
 #define mp_hal_pin_toggle(p) (GPIO_PortToggle(p->gpio, (1 << p->pin)))
 #define mp_hal_pin_read(p) (GPIO_PinReadPadStatus(p->gpio, p->pin))
@@ -72,8 +73,16 @@ static inline void mp_hal_delay_us(mp_uint_t us) {
 
 #define mp_hal_delay_us_fast(us) mp_hal_delay_us(us)
 
+static inline void mp_hal_ticks_cpu_init(void) {
+    DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+}
+
 static inline mp_uint_t mp_hal_ticks_cpu(void) {
-    return 0;
+    return DWT->CYCCNT;
+}
+
+static inline mp_uint_t mp_hal_get_cpu_freq(void) {
+    return CLOCK_GetCpuClkFreq();
 }