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spi: Add SPI transfer function that pass in RX/TX

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When using SPI, I prefer to not have to do malloc/free functions for each
transfer, so why not have a transfer function that you can pass in both
buffers.  With my ILI9341 TFT display code that gave some perf wins, also more
of a win, you can pass in NULL for recv buffer and the underlying device driver
does not have to copy the data.

Signed-off-by: Kurt Eckhardt <kurte@rockisland.com>
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
This commit is contained in:
Kurt Eckhardt
2014-10-18 09:25:19 -07:00
committed by Brendan Le Foll
parent 54deb01796
commit 2a11e31052
4 changed files with 53 additions and 5 deletions
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11
api/mraa/spi.h
View File

@@ -105,6 +105,17 @@ uint8_t mraa_spi_write(mraa_spi_context dev, uint8_t data);
*/
uint8_t* mraa_spi_write_buf(mraa_spi_context dev, uint8_t* data, int length);
/** Transfer Buffer of bytes to the SPI device. Both send and recv buffers
* are passed in
*
* @param dev The Spi context
* @param data to send
* @param rxbuf buffer to recv data back, may be NULL
* @param length elements within buffer, Max 4096
* @return Result of operation
*/
mraa_result_t mraa_spi_transfer_buf(mraa_spi_context dev, uint8_t* data, uint8_t* rxbuf, int length);
/**
* Change the SPI lsb mode
*

15
api/mraa/spi.hpp
View File

@@ -84,7 +84,8 @@ class Spi {
return (char) mraa_spi_write(m_spi, (uint8_t) data);
}
/**
* Write buffer of bytes to SPI device
* Write buffer of bytes to SPI device The pointer return has to be
* free'd by the caller.
*
* @param data buffer to send
* @param length size of buffer to send
@@ -93,6 +94,18 @@ class Spi {
char* write(char* data, size_t length) {
return (char*) mraa_spi_write_buf(m_spi, (uint8_t *) data, (int) length);
}
/**
* Transfer data to and from SPI device Receive pointer may be null if return
* data is not needed.
*
* @param data buffer to send
* @param rxBuf buffer to optionally receive data from spi device
* @param length size of buffer to send
* @return Result of operation
*/
mraa_result_t transfer(char* data, char* rxBuf, size_t length) {
return mraa_spi_transfer_buf(m_spi, (uint8_t *) data, (uint8_t *)rxBuf, (int) length);
}
/**
* Change the SPI lsb mode
*

13
examples/c++/Spi-pot.cpp
View File

@@ -49,6 +49,7 @@ int main ()
spi = new mraa::Spi(0);
char data[] = {0x00, 100};
char rxBuf[2];
char *recv;
while (running == 0) {
int i;
@@ -56,14 +57,18 @@ int main ()
data[1] = i;
recv = spi->write(data, 2);
printf("Writing -%i",i);
printf("RECIVED-%i-%i\n",recv[0],recv[1]);
if (recv) {
printf("RECIVED-%i-%i\n",recv[0],recv[1]);
free(recv);
}
usleep(100000);
}
for (i = 130; i > 90; i--) {
data[1] = i;
recv = spi->write(data, 2);
printf("Writing -%i",i);
printf("RECIVED-%i-%i\n",recv[0],recv[1]);
if (spi->transfer(data, rxBuf, 2) == MRAA_SUCCESS) {
printf("Writing -%i",i);
printf("RECIVED-%i-%i\n",rxBuf[0],rxBuf[1]);
}
usleep(100000);
}

19
src/spi/spi.c
View File

@@ -193,6 +193,25 @@ mraa_spi_write_buf(mraa_spi_context dev, uint8_t* data, int length)
return recv;
}
mraa_result_t
mraa_spi_transfer_buf(mraa_spi_context dev, uint8_t* data, uint8_t* rxbuf, int length)
{
struct spi_ioc_transfer msg;
memset(&msg, 0, sizeof(msg));
msg.tx_buf = (unsigned long) data;
msg.rx_buf = (unsigned long) rxbuf;
msg.speed_hz = dev->clock;
msg.bits_per_word = dev->bpw;
msg.delay_usecs = 0;
msg.len = length;
if (ioctl(dev->devfd, SPI_IOC_MESSAGE(1), &msg) < 0) {
syslog(LOG_ERR, "Failed to perform dev transfer");
return MRAA_ERROR_INVALID_RESOURCE;
}
return MRAA_SUCCESS;
}
mraa_result_t
mraa_spi_stop(mraa_spi_context dev)
{