How to make a single function from repetitive code? - c

Question

I'm writing some code for my embedded system. As I'm adding more different channels of the same periphery, I'm getting code that's really repetitive. For example:
void pos1_write_read(int *pwriteData)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf0, 0, m_length0);
spi0_xfer_done = false;
nrfx_spi_xfer_desc_t m_pos1_write;
m_pos1_write.p_tx_buffer = pwriteData;
m_pos1_write.tx_length = m_length0;
m_pos1_write.p_rx_buffer = m_rx_buf0;
m_pos1_write.rx_length = m_length0;
nrf_gpio_pin_clear(SPI0_CS0_PIN); //Set CS0 to 0 (on)
APP_ERROR_CHECK(nrfx_spi_xfer(&spi0, &spi0_transfer, NULL));
while (!spi0_xfer_done){} //Wait until the tranfser is done
nrf_gpio_pin_set(SPI0_CS0_PIN); //Set CS0 to 1 (off)
}
void pos2_write_read(int *pwriteData)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf0, 0, m_length0);
spi0_xfer_done = false;
nrfx_spi_xfer_desc_t m_pos2_write;
m_pos2_write.p_tx_buffer = pwriteData;
m_pos2_write.tx_length = m_length0;
m_pos2_write.p_rx_buffer = m_rx_buf0;
m_pos2_write.rx_length = m_length0;
nrf_gpio_pin_clear(SPI0_CS1_PIN); //Set CS1 to 0 (on)
APP_ERROR_CHECK(nrfx_spi_xfer(&spi0, &spi0_transfer, NULL));
while (!spi0_xfer_done){} //Wait until the tranfser is done
nrf_gpio_pin_set(SPI0_CS1_PIN); //Set CS1 to 1 (off)
}
How would I write a single function that could be used in both examples? Is there any general good practice to avoid repeating the same code?

Answer 1

Finding the right design depends on how it's intended to be used, how generic you feel is appropriate, etc. There is no single correct way to do this. But the naive solution based only on your code snippet is something like:
void write_read(int *pwriteData, int pin)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf0, 0, m_length0);
spi0_xfer_done = false;
nrfx_spi_xfer_desc_t m_pos1_write;
m_pos1_write.p_tx_buffer = pwriteData;
m_pos1_write.tx_length = m_length0;
m_pos1_write.p_rx_buffer = m_rx_buf0;
m_pos1_write.rx_length = m_length0;
nrf_gpio_pin_clear(pin); //Set CS0 to 0 (on)
APP_ERROR_CHECK(nrfx_spi_xfer(&spi0, &spi0_transfer, NULL));
while (!spi0_xfer_done){} //Wait until the tranfser is done
nrf_gpio_pin_set(pin); //Set CS0 to 1 (off)
}
void pos1_write_read(int *pwriteData)
{
write_read(pwriteData, SPI0_CS0_PIN);
}
void pos2_write_read(int *pwriteData)
{
write_read(pwriteData, SPI0_CS1_PIN);
}
The idea is to just take the common code, and parameterize anything that's different between them.

Answer 2

The only real difference is the SC pin, which you can pass as an argument:
void pos_write_read(int *pwriteData, uint32_t pin)
{
// Reset rx buffer and transfer done flag
memset(m_rx_buf0, 0, m_length0);
spi0_xfer_done = false;
nrfx_spi_xfer_desc_t m_pos_write;
m_pos_write.p_tx_buffer = pwriteData;
m_pos_write.tx_length = m_length0;
m_pos_write.p_rx_buffer = m_rx_buf0;
m_pos_write.rx_length = m_length0;
nrf_gpio_pin_clear(pin); //Set CS to 0 (on)
APP_ERROR_CHECK(nrfx_spi_xfer(&spi0, &spi0_transfer, NULL));
while (!spi0_xfer_done){} //Wait until the tranfser is done
nrf_gpio_pin_set(pin); //Set CS to 1 (off)
}
/* This allows you to do the following: */
void pos1_write_read(int *pwriteData)
{
pos_write_read(pwriteData, SPI0_CS0_PIN);
}
void pos2_write_read(int *pwriteData)
{
pos_write_read(pwriteData, SPI0_CS1_PIN);
}