Hi,
I have implemented a hx711 sensor readout with PPI, using SPIM and PWM peripherals. But for this is needed 4 GPIO and one external OR Gate. I wait for a LOW pulse on AL_SPIM_MISO_PIN, and Read SPI data and disable pulse detect. When SPI RX end, I put and extra pulse in ALT_SPIM_SCK_PIN (I only want Channel A with 128 Gain) and enable again pulse detect.
This is the code:
static void spi_init_hx711(void)
{
nrfx_spim_xfer_desc_t xfer_desc = NRFX_SPIM_XFER_TRX(tx_buffer_spi, LS7366_SPI_BUFFER_SIZE, rx_buffer_spi, LS7366_SPI_BUFFER_SIZE);
nrfx_spim_config_t spi_config = NRFX_SPIM_DEFAULT_CONFIG;
spi_config.frequency = NRF_SPIM_FREQ_500K;
spi_config.ss_pin = SPIM_SS_PIN;
spi_config.miso_pin = SPIM_MISO_PIN;
spi_config.mosi_pin = SPIM_MOSI_PIN;
spi_config.sck_pin = SPIM_SCK_PIN;
///spi_config.mode = NRF_SPIM_MODE_1;
spi_config.use_hw_ss = true;
spi_config.ss_active_high = false;
ret_code_t err_code = nrfx_spim_init(&spi, &spi_config, spim_event_handler, NULL);
APP_ERROR_CHECK(err_code);
}
void spim_event_handler(nrfx_spim_evt_t const * p_event,
void * p_context)
{
if(p_event->type == NRFX_SPIM_EVENT_DONE)
{
NRF_LOG_DEBUG("TxDone\n");
NRF_LOG_HEXDUMP_INFO(rx_buffer_spi,LS7366_SPI_BUFFER_SIZE);
spi_tx_done = true;
}
else
{
NRF_LOG_DEBUG("Wrong Event\n");
// Something is wrong
}
}
static void hx711_spi_sampling_event_config()
{
ret_code_t err_code;
err_code = nrf_drv_ppi_init();
APP_ERROR_CHECK(err_code);
uint32_t spi_evt_addr;
uint32_t spi_task_addr;
uint32_t data_in_evt_addr;
uint32_t put_clk_pulses_task_addr;
uint32_t disable_ppi_channel_start_task_addr;
uint32_t enable_ppi_channel_group_task_addr;
err_code = nrfx_ppi_channel_alloc(&m_ppi_channel_detect_hx711_start_tx); //Detect TX Ready
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_channel_alloc(&m_ppi_channel_stop_spi);
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_group_alloc(&m_ppi_group_hx711);
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_channel_include_in_group(m_ppi_channel_detect_hx711_start_tx, NRF_PPI_CHANNEL_GROUP0);
APP_ERROR_CHECK(err_code);
data_in_evt_addr = nrfx_gpiote_in_event_addr_get(ALT_SPIM_MISO_PIN); //DATAIN going low detect
static uint16_t seq_values[] ={0};
nrf_pwm_sequence_t const seq =
{
.values.p_common = seq_values,
.length = NRF_PWM_VALUES_LENGTH(seq_values),
.repeats = 1,
.end_delay = 0
};
spi_task_addr = nrfx_spim_start_task_get(&spi); //SPI START task address
put_clk_pulses_task_addr = nrfx_pwm_simple_playback(&m_pwm1, &seq, 1,
NRFX_PWM_FLAG_STOP |
NRFX_PWM_FLAG_START_VIA_TASK);
disable_ppi_channel_start_task_addr = nrfx_ppi_task_addr_get(NRF_PPI_TASK_CHG0_DIS);
//1ST PPI CHANNEL
err_code = nrfx_ppi_channel_assign(m_ppi_channel_detect_hx711_start_tx,
data_in_evt_addr,
spi_task_addr); //Start SPI RX
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_channel_fork_assign(m_ppi_channel_detect_hx711_start_tx,
disable_ppi_channel_start_task_addr); //Disable DIN Detect
APP_ERROR_CHECK(err_code);
//2ND PPI CHANNEL
spi_evt_addr = nrfx_spim_end_event_get(&spi);
enable_ppi_channel_group_task_addr = nrfx_ppi_task_addr_get(NRF_PPI_TASK_CHG0_EN);
err_code = nrfx_ppi_channel_assign(m_ppi_channel_stop_spi,
spi_evt_addr,
put_clk_pulses_task_addr); //Put Extra pulses
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_channel_fork_assign(m_ppi_channel_stop_spi, enable_ppi_channel_group_task_addr); //Renable MISO go down detection
APP_ERROR_CHECK(err_code);
}
static void hx711_spi_init()
{
ret_code_t err_code = nrfx_ppi_channel_enable(m_ppi_channel_detect_hx711_start_tx);
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_group_enable(m_ppi_group_hx711);
APP_ERROR_CHECK(err_code);
err_code = nrfx_ppi_channel_enable(m_ppi_channel_stop_spi);
APP_ERROR_CHECK(err_code);
nrfx_gpiote_in_event_enable(ALT_SPIM_MISO_PIN, true);
}
static void pwm_init()
{
uint32_t err_code;
// Config the pwm to set additional pulses in SPI
nrfx_pwm_config_t const config1 =
{
.output_pins =
{
ALT_SPIM_SCK_PIN, // channel 0
NRFX_PWM_PIN_NOT_USED, // channel 1
NRFX_PWM_PIN_NOT_USED, // channel 2
NRFX_PWM_PIN_NOT_USED, // channel 3
},
.irq_priority = APP_IRQ_PRIORITY_HIGH,
.base_clock = NRF_PWM_CLK_2MHz,
.count_mode = NRF_PWM_MODE_UP,
.top_value = 1,
.load_mode = NRF_PWM_LOAD_COMMON,
.step_mode = NRF_PWM_STEP_AUTO
};
err_code = nrfx_pwm_init(&m_pwm1, &config1, NULL);
}
static void spi_prepare_transfer(void)
{
tx_buffer_spi[0] = 0xAA; //Dont worry about this number
memset(rx_buffer_spi,0,3);
nrfx_spim_xfer_desc_t xfer = NRFX_SPIM_XFER_TRX(tx_buffer_spi, 1, rx_buffer_spi, 3);
uint32_t flags = NRFX_SPIM_FLAG_HOLD_XFER | NRFX_SPIM_FLAG_REPEATED_XFER | NRFX_SPIM_FLAG_NO_XFER_EVT_HANDLER;
nrfx_spim_xfer(&spi, &xfer, flags);
}
int main(void)
{
(...)
spi_init_hx711();
pwm_init();
hx711_spi_sampling_event_config();
hx711_spi_init();
(...)
}
How can i delete the OR Gate, or extra PINs?
Thank you.
