bitbangio.SPI.read: Support write_value, fix some other nits

shared-bindings/bitbangio/SPI.c

@@ -224,32 +224,53 @@ STATIC mp_obj_t bitbangio_spi_write(mp_obj_t self_in, mp_obj_t wr_buf) {
 MP_DEFINE_CONST_FUN_OBJ_2(bitbangio_spi_write_obj, bitbangio_spi_write);
 
 
-//|     def readinto(self, buf: WriteableBuffer) -> None:
+//|     def readinto(self, buffer: WriteableBuffer, *, start: int = 0, end: Optional[int] = None, write_value: int = 0) -> None:
-//|         """Read into the buffer specified by ``buf`` while writing zeroes.
+//|         """Read into ``buffer`` while writing ``write_value`` for each byte read.
-//|         Requires the SPI being locked.
+//|         The SPI object must be locked.
-//|         If the number of bytes to read is 0, nothing happens."""
+//|         If the number of bytes to read is 0, nothing happens.
+//|
+//|         :param bytearray buffer: Read data into this buffer
+//|         :param int start: Start of the slice of ``buffer`` to read into: ``buffer[start:end]``
+//|         :param int end: End of the slice; this index is not included. Defaults to ``len(buffer)``
+//|         :param int write_value: Value to write while reading."""
 //|         ...
 //|
-// TODO(tannewt): Add support for start and end kwargs.
+
-STATIC mp_obj_t bitbangio_spi_readinto(size_t n_args, const mp_obj_t *args) {
+STATIC mp_obj_t bitbangio_spi_readinto(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    bitbangio_spi_obj_t *self = MP_OBJ_TO_PTR(args[0]);
+    enum { ARG_buffer, ARG_start, ARG_end, ARG_write_value };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_buffer,     MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_start,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_end,        MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = INT_MAX} },
+        { MP_QSTR_write_value,MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+    };
+    bitbangio_spi_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
     check_for_deinit(self);
+    check_lock(self);
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
     mp_buffer_info_t bufinfo;
-    mp_get_buffer_raise(args[1], &bufinfo, MP_BUFFER_WRITE);
+    mp_get_buffer_raise(args[ARG_buffer].u_obj, &bufinfo, MP_BUFFER_WRITE);
-    if (bufinfo.len == 0) {
+    int32_t start = args[ARG_start].u_int;
+    size_t length = bufinfo.len;
+    normalize_buffer_bounds(&start, args[ARG_end].u_int, &length);
+
+    if (length == 0) {
         return mp_const_none;
     }
-    check_lock(args[0]);
+
-    bool ok = shared_module_bitbangio_spi_read(self, bufinfo.buf, bufinfo.len);
+    bool ok = shared_module_bitbangio_spi_read(self, ((uint8_t*)bufinfo.buf) + start, length, args[ARG_write_value].u_int);
     if (!ok) {
         mp_raise_OSError(MP_EIO);
     }
     return mp_const_none;
 }
-MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(bitbangio_spi_readinto_obj, 2, 2, bitbangio_spi_readinto);
+MP_DEFINE_CONST_FUN_OBJ_KW(bitbangio_spi_readinto_obj, 2, bitbangio_spi_readinto);
 
-//|     def write_readinto(self, buffer_out: ReadableBuffer, buffer_in: WriteableBuffer, *, out_start: int = 0, out_end: Optional[int] = None, in_start: int = 0, in_end: Optional[int] = None) -> None:
+//|     def write_readinto(self, buffer_out: ReadableBuffer, buffer_in: ReadableBuffer, *, out_start: int = 0, out_end: Optional[int] = None, in_start: int = 0, in_end: Optional[int] = None) -> None:
 //|         """Write out the data in ``buffer_out`` while simultaneously reading data into ``buffer_in``.
+//|         The SPI object must be locked.
 //|         The lengths of the slices defined by ``buffer_out[out_start:out_end]`` and ``buffer_in[in_start:in_end]``
 //|         must be equal.
 //|         If buffer slice lengths are both 0, nothing happens.
@@ -274,6 +295,7 @@ STATIC mp_obj_t bitbangio_spi_write_readinto(size_t n_args, const mp_obj_t *pos_
     };
     bitbangio_spi_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
     check_for_deinit(self);
+    check_lock(self);
 
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);

shared-bindings/bitbangio/SPI.h

@@ -54,7 +54,7 @@ extern void shared_module_bitbangio_spi_unlock(bitbangio_spi_obj_t *self);
 extern bool shared_module_bitbangio_spi_write(bitbangio_spi_obj_t *self, const uint8_t *data, size_t len);
 
 // Reads in len bytes while outputting zeroes.
-extern bool shared_module_bitbangio_spi_read(bitbangio_spi_obj_t *self, uint8_t *data, size_t len);
+extern bool shared_module_bitbangio_spi_read(bitbangio_spi_obj_t *self, uint8_t *data, size_t len, uint8_t write_value);
 
 // Transfer out len bytes while reading len bytes
 extern bool shared_module_bitbangio_spi_transfer(bitbangio_spi_obj_t *self, const uint8_t *dout, uint8_t *din, size_t len);

shared-module/bitbangio/SPI.c

@@ -176,7 +176,7 @@ bool shared_module_bitbangio_spi_write(bitbangio_spi_obj_t *self, const uint8_t
 }
 
 // Reads in len bytes while outputting zeroes.
-bool shared_module_bitbangio_spi_read(bitbangio_spi_obj_t *self, uint8_t *data, size_t len) {
+bool shared_module_bitbangio_spi_read(bitbangio_spi_obj_t *self, uint8_t *data, size_t len, uint8_t write_data) {
     if (len > 0 && !self->has_miso) {
         mp_raise_ValueError(translate("Cannot read without MISO pin."));
     }
@@ -210,8 +210,12 @@ bool shared_module_bitbangio_spi_read(bitbangio_spi_obj_t *self, uint8_t *data,
         common_hal_digitalio_digitalinout_set_value(&self->mosi, false);
     }
     for (size_t i = 0; i < len; ++i) {
+        uint8_t data_out = write_data;
         uint8_t data_in = 0;
-        for (int j = 0; j < 8; ++j) {
+        for (int j = 0; j < 8; ++j, data_out <<= 1) {
+            if (self->has_mosi) {
+                common_hal_digitalio_digitalinout_set_value(&self->mosi, (data_out >> 7) & 1);
+            }
             if (self->phase == 0) {
                 common_hal_mcu_delay_us(delay_half);
                 common_hal_digitalio_digitalinout_set_value(&self->clock, 1 - self->polarity);