add SPI.write_readinto() - bidirectional SPI

5 files changed, 103 insertions, 15 deletions

diff --git a/atmel-samd/common-hal/busio/SPI.c b/atmel-samd/common-hal/busio/SPI.c
index c1b13cec8..e5a945df2 100644
--- a/atmel-samd/common-hal/busio/SPI.c
+++ b/atmel-samd/common-hal/busio/SPI.c
@@ -257,3 +257,16 @@ bool common_hal_busio_spi_read(busio_spi_obj_t *self,
     }
     return status == STATUS_OK;
 }
+
+bool common_hal_busio_spi_transfer(busio_spi_obj_t *self, uint8_t *data_out, uint8_t *data_in, size_t len) {
+    if (len == 0) {
+        return true;
+    }
+    enum status_code status;
+    if (len >= 16) {
+        status = shared_dma_transfer(self->spi_master_instance.hw, data_out, data_in, len, 0 /*ignored*/);
+    } else {
+        status = spi_transceive_buffer_wait(&self->spi_master_instance, data_out, data_in, len);
+    }
+    return status == STATUS_OK;
+}
diff --git a/atmel-samd/shared_dma.c b/atmel-samd/shared_dma.c
index 461798366..c0f0d4672 100644
--- a/atmel-samd/shared_dma.c
+++ b/atmel-samd/shared_dma.c
@@ -103,7 +103,7 @@ enum status_code shared_dma_write(Sercom* sercom, const uint8_t* buffer, uint32_
     }
     dma_configure(general_dma_tx.channel_id, sercom_index(sercom) * 2 + 2, false);
 
-    // Set up TX second.
+    // Set up TX. There is no RX job.
     struct dma_descriptor_config descriptor_config;
     dma_descriptor_get_config_defaults(&descriptor_config);
     descriptor_config.beat_size = DMA_BEAT_SIZE_BYTE;
@@ -137,6 +137,12 @@ enum status_code shared_dma_write(Sercom* sercom, const uint8_t* buffer, uint32_
 }
 
 enum status_code shared_dma_read(Sercom* sercom, uint8_t* buffer, uint32_t length, uint8_t tx) {
+    return shared_dma_transfer(sercom, NULL, buffer, length, tx);
+}
+
+// Do write and read simultaneously. If buffer_out is NULL, write the tx byte over and over.
+// If buffer_out is a real buffer, ignore tx.
+enum status_code shared_dma_transfer(Sercom* sercom, uint8_t* buffer_out, uint8_t* buffer_in, uint32_t length, uint8_t tx) {
     if (general_dma_tx.job_status != STATUS_OK) {
         return general_dma_tx.job_status;
     }
@@ -153,17 +159,19 @@ enum status_code shared_dma_read(Sercom* sercom, uint8_t* buffer, uint32_t lengt
     descriptor_config.block_transfer_count = length;
     // DATA register is consistently addressed across all SERCOM modes.
     descriptor_config.source_address = ((uint32_t)&sercom->SPI.DATA.reg);
-    descriptor_config.destination_address = ((uint32_t)buffer + length);
+    descriptor_config.destination_address = ((uint32_t)buffer_in + length);
 
     dma_descriptor_create(general_dma_rx.descriptor, &descriptor_config);
 
-    // Set up TX to retransmit the same byte over and over.
+    // Set up TX second.
     dma_descriptor_get_config_defaults(&descriptor_config);
     descriptor_config.beat_size = DMA_BEAT_SIZE_BYTE;
-    descriptor_config.src_increment_enable = false;
+    // Increment write address only if we have a real buffer.
+    descriptor_config.src_increment_enable = buffer_out != NULL;
     descriptor_config.dst_increment_enable = false;
     descriptor_config.block_transfer_count = length;
-    descriptor_config.source_address = ((uint32_t)&tx);
+    // 
+    descriptor_config.source_address = ((uint32_t) (buffer_out != NULL ? buffer_out + length : &tx));
     // DATA register is consistently addressed across all SERCOM modes.
     descriptor_config.destination_address = ((uint32_t)&sercom->SPI.DATA.reg);
 
diff --git a/atmel-samd/shared_dma.h b/atmel-samd/shared_dma.h
index 7aa45547d..251b8357b 100644
--- a/atmel-samd/shared_dma.h
+++ b/atmel-samd/shared_dma.h
@@ -39,6 +39,7 @@ void init_shared_dma(void);
 
 enum status_code shared_dma_write(Sercom* sercom, const uint8_t* buffer, uint32_t length);
 enum status_code shared_dma_read(Sercom* sercom, uint8_t* buffer, uint32_t length, uint8_t tx);
+enum status_code shared_dma_transfer(Sercom* sercom, uint8_t* buffer_out, uint8_t* buffer_in, uint32_t length, uint8_t tx);
 
 // Allocate a counter to track how far along we are in a DMA double buffer.
 bool allocate_block_counter(void);
diff --git a/shared-bindings/busio/SPI.c b/shared-bindings/busio/SPI.c
index 72787af30..c4c139105 100644
--- a/shared-bindings/busio/SPI.c
+++ b/shared-bindings/busio/SPI.c
@@ -206,12 +206,12 @@ MP_DEFINE_CONST_FUN_OBJ_1(busio_spi_unlock_obj, busio_spi_obj_unlock);
 
 //|   .. method:: SPI.write(buffer, \*, start=0, end=len(buffer))
 //|
-//|     Write the data contained in ``buf``. Requires the SPI being locked.
+//|     Write the data contained in ``buffer``. The SPI object must be locked.
 //|     If the buffer is empty, nothing happens.
 //|
-//|     :param bytearray buffer: buffer containing the bytes to write
-//|     :param int start: Index to start writing from
-//|     :param int end: Index to read up to but not include
+//|     :param bytearray buffer: Write out the data in this buffer
+//|     :param int start: Start of the slice of ``buffer`` to write out: ``buffer[start:end]``
+//|     :param int end: End of the slice; this index is not included
 //|
 STATIC mp_obj_t busio_spi_write(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_buffer, ARG_start, ARG_end };
@@ -247,14 +247,14 @@ MP_DEFINE_CONST_FUN_OBJ_KW(busio_spi_write_obj, 2, busio_spi_write);
 
 //|   .. method:: SPI.readinto(buffer, \*, start=0, end=len(buffer), write_value=0)
 //|
-//|     Read into the buffer specified by ``buf`` while writing zeroes.
-//|     Requires the SPI being locked.
+//|     Read into ``buffer`` while writing ``write_value`` for each byte read.
+//|     The SPI object must be locked.
 //|     If the number of bytes to read is 0, nothing happens.
 //|
-//|     :param bytearray buffer: buffer to write into
-//|     :param int start: Index to start writing at
-//|     :param int end: Index to write up to but not include
-//|     :param int write_value: Value to write reading. (Usually ignored.)
+//|     :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 
+//|     :param int write_value: Value to write while reading. (Usually ignored.)
 //|
 STATIC mp_obj_t busio_spi_readinto(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     enum { ARG_buffer, ARG_start, ARG_end, ARG_write_value };
@@ -288,6 +288,68 @@ STATIC mp_obj_t busio_spi_readinto(size_t n_args, const mp_obj_t *pos_args, mp_m
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(busio_spi_readinto_obj, 2, busio_spi_readinto);
 
+//|   .. method:: SPI.write_readinto(buffer_out, buffer_in, \*, out_start=0, out_end=len(buffer_out), in_start=0, in_end=len(buffer_in))
+//|
+//|     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.
+//|
+//|     :param bytearray buffer_out: Write out the data in this buffer
+//|     :param bytearray buffer_in: Read data into this buffer
+//|     :param int out_start: Start of the slice of buffer_out to write out: ``buffer_out[out_start:out_end]``
+//|     :param int out_end: End of the slice; this index is not included 
+//|     :param int in_start: Start of the slice of ``buffer_in`` to read into: ``buffer_in[in_start:in_end]``
+//|     :param int in_end: End of the slice; this index is not included
+//|
+STATIC mp_obj_t busio_spi_write_readinto(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_buffer_out, ARG_buffer_in, ARG_out_start, ARG_out_end, ARG_in_start, ARG_in_end };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_buffer_out,    MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_buffer_in,     MP_ARG_REQUIRED | MP_ARG_OBJ, {.u_obj = MP_OBJ_NULL} },
+        { MP_QSTR_out_start,     MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_out_end,       MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = INT_MAX} },
+        { MP_QSTR_in_start,      MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = 0} },
+        { MP_QSTR_in_end,        MP_ARG_KW_ONLY | MP_ARG_INT, {.u_int = INT_MAX} },
+    };
+    busio_spi_obj_t *self = MP_OBJ_TO_PTR(pos_args[0]);
+    raise_error_if_deinited(common_hal_busio_spi_deinited(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 buf_out_info;
+    mp_get_buffer_raise(args[ARG_buffer_out].u_obj, &buf_out_info, MP_BUFFER_READ);
+    int32_t out_start = args[ARG_out_start].u_int;
+    uint32_t out_length = buf_out_info.len;
+    normalize_buffer_bounds(&out_start, args[ARG_out_end].u_int, &out_length);
+
+    mp_buffer_info_t buf_in_info;
+    mp_get_buffer_raise(args[ARG_buffer_in].u_obj, &buf_in_info, MP_BUFFER_WRITE);
+    int32_t in_start = args[ARG_in_start].u_int;
+    uint32_t in_length = buf_in_info.len;
+    normalize_buffer_bounds(&in_start, args[ARG_in_end].u_int, &in_length);
+
+    if (out_length != in_length) {
+        mp_raise_ValueError("buffer slices must be of equal length");
+    }
+
+    if (out_length == 0) {
+        return mp_const_none;
+    }
+
+    bool ok = common_hal_busio_spi_transfer(self,
+                                            ((uint8_t*)buf_out_info.buf) + out_start,
+                                            ((uint8_t*)buf_in_info.buf) + in_start,
+                                            out_length);
+    if (!ok) {
+        mp_raise_OSError(MP_EIO);
+    }
+    return mp_const_none;
+}
+MP_DEFINE_CONST_FUN_OBJ_KW(busio_spi_write_readinto_obj, 2, busio_spi_write_readinto);
+
 STATIC const mp_rom_map_elem_t busio_spi_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&busio_spi_deinit_obj) },
     { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&default___enter___obj) },
@@ -299,6 +361,7 @@ STATIC const mp_rom_map_elem_t busio_spi_locals_dict_table[] = {
 
     { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&busio_spi_readinto_obj) },
     { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&busio_spi_write_obj) },
+    { MP_ROM_QSTR(MP_QSTR_write_readinto), MP_ROM_PTR(&busio_spi_write_readinto_obj) },
 };
 STATIC MP_DEFINE_CONST_DICT(busio_spi_locals_dict, busio_spi_locals_dict_table);
 
diff --git a/shared-bindings/busio/SPI.h b/shared-bindings/busio/SPI.h
index ac31d5060..b6e5c9b1b 100644
--- a/shared-bindings/busio/SPI.h
+++ b/shared-bindings/busio/SPI.h
@@ -55,4 +55,7 @@ extern bool common_hal_busio_spi_write(busio_spi_obj_t *self, const uint8_t *dat
 // Reads in len bytes while outputting zeroes.
 extern bool common_hal_busio_spi_read(busio_spi_obj_t *self, uint8_t *data, size_t len, uint8_t write_value);
 
+// Reads and write len bytes simultaneously.
+extern bool common_hal_busio_spi_transfer(busio_spi_obj_t *self, uint8_t *data_out, uint8_t *data_in, size_t len);
+
 #endif // MICROPY_INCLUDED_SHARED_BINDINGS_BUSIO_SPI_H