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drivers: CAN: MCP2515: Add and use Load TX Buffer instruction

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Reduces SPI data for loading TX buffer by 1 byte

Signed-off-by: Nick Ward <nix.ward@gmail.com>
This commit is contained in:
Nick Ward 2019-08-08 00:08:08 +10:00 • committed by Jukka Rissanen
commit 4816d06cfb
2 changed files with 41 additions and 4 deletions
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44
drivers/can/can_mcp2515.c
View file

@ -60,6 +60,38 @@ static int mcp2515_cmd_write_reg(struct device *dev, u8_t reg_addr,
return spi_write(DEV_DATA(dev)->spi, &DEV_DATA(dev)->spi_cfg, &tx);
}
/*
* Load TX buffer instruction
*
* When loading a transmit buffer, reduces the overhead of a normal WRITE
* command by placing the Address Pointer at one of six locations, as
* selected by parameter abc.
*
* 0: TX Buffer 0, Start at TXB0SIDH (0x31)
* 1: TX Buffer 0, Start at TXB0D0 (0x36)
* 2: TX Buffer 1, Start at TXB1SIDH (0x41)
* 3: TX Buffer 1, Start at TXB1D0 (0x46)
* 4: TX Buffer 2, Start at TXB2SIDH (0x51)
* 5: TX Buffer 2, Start at TXB2D0 (0x56)
*/
static int mcp2515_cmd_load_tx_buffer(struct device *dev, u8_t abc,
u8_t *buf_data, u8_t buf_len)
{
__ASSERT(abc <= 5, "abc <= 5");
u8_t cmd_buf[] = { MCP2515_OPCODE_LOAD_TX_BUFFER | abc };
struct spi_buf tx_buf[] = {
{ .buf = cmd_buf, .len = sizeof(cmd_buf) },
{ .buf = buf_data, .len = buf_len }
};
const struct spi_buf_set tx = {
.buffers = tx_buf, .count = ARRAY_SIZE(tx_buf)
};
return spi_write(DEV_DATA(dev)->spi, &DEV_DATA(dev)->spi_cfg, &tx);
}
static int mcp2515_cmd_read_reg(struct device *dev, u8_t reg_addr,
u8_t *buf_data, u8_t buf_len)
{
@ -292,6 +324,7 @@ static int mcp2515_send(struct device *dev, const struct zcan_frame *msg,
{
struct mcp2515_data *dev_data = DEV_DATA(dev);
u8_t tx_idx = 0U;
u8_t abc;
u8_t addr_tx_ctrl;
u8_t tx_frame[MCP2515_FRAME_LEN];
@ -323,9 +356,12 @@ static int mcp2515_send(struct device *dev, const struct zcan_frame *msg,
(tx_idx * MCP2515_ADDR_OFFSET_FRAME2FRAME);
mcp2515_convert_zcanframe_to_mcp2515frame(msg, tx_frame);
mcp2515_cmd_write_reg(dev,
addr_tx_ctrl + MCP2515_ADDR_OFFSET_CTRL2FRAME,
tx_frame, sizeof(tx_frame));
/* Address Pointer selection */
abc = 2 * tx_idx;
mcp2515_cmd_load_tx_buffer(dev, abc, tx_frame, sizeof(tx_frame));
/* request tx slot transmission */
mcp2515_cmd_bit_modify(dev, addr_tx_ctrl, MCP2515_TXCTRL_TXREQ,
MCP2515_TXCTRL_TXREQ);
@ -632,7 +668,7 @@ static int mcp2515_init(struct device *dev)
k_sem_init(&dev_data->int_sem, 0, 1);
k_mutex_init(&dev_data->mutex);
k_sem_init(&dev_data->tx_sem, 3, 3);
k_sem_init(&dev_data->tx_sem, MCP2515_TX_CNT, MCP2515_TX_CNT);
k_sem_init(&dev_data->tx_cb[0].sem, 0, 1);
k_sem_init(&dev_data->tx_cb[1].sem, 0, 1);
k_sem_init(&dev_data->tx_cb[2].sem, 0, 1);

1
drivers/can/can_mcp2515.h
View file

@ -82,6 +82,7 @@ struct mcp2515_config {
#define MCP2515_OPCODE_WRITE 0x02
#define MCP2515_OPCODE_READ 0x03
#define MCP2515_OPCODE_BIT_MODIFY 0x05
#define MCP2515_OPCODE_LOAD_TX_BUFFER 0x40
#define MCP2515_OPCODE_READ_STATUS 0xA0
#define MCP2515_OPCODE_RESET 0xC0