How to get command/data on I2C Slave, which has been send from I2C master.

RE: How to get command/data on I2C Slave, which has been send from I2C master.

Jørgen Holmefjord — Wed, 29 Apr 2020 10:09:17 GMT

That code seems to do nothing TWIS-related. I was thinking something in the line of this (not compiled/tested):

#define TWIS_MAX_LENGHT 20
uint8_t tx_buffer[TWIS_MAX_LENGHT] = {0};
uint8_t rx_buffer[TWIS_MAX_LENGHT] = {0};

uint8_t rx_length = 0;

uint8_t command1[4] = {0xA1, 0xA2, 0x01, 0x02};
uint8_t command2[2] = {0xA4, 0xA5};

uint8_t command1_response[16] = {0x00};
uint8_t command2_response[8] = {0x55};
  
static void twis_event_handler(nrf_drv_twis_evt_t const * const p_event)
{
	debug_printf(" \nevent handler");
	switch (p_event->type)
	{
	case TWIS_EVT_READ_REQ:
		if (p_event->data.buf_req)
		{
		nrf_drv_twis_tx_prepare(&m_twis, tx_buffer, TWIS_MAX_LENGHT);
		}
		break;
	case TWIS_EVT_READ_DONE:
		if(p_event->data.tx_amount == 4 && memcmp(tx_buffer, command1, 4) == 0)
		{
			// Fill rx_buffer with correct response for command1
			memcpy(rx_buffer, command1_response, sizeof(command1_response));
			rx_length = sizeof(command1_response);
		}
		else if(p_event->data.tx_amount == 2 && memcmp(tx_buffer, command2, 2) == 0)
		{
			// Fill rx_buffer with correct response for command2
			memcpy(rx_buffer, command2_response, sizeof(command2_response));
			rx_length = sizeof(command2_response);
		}
		else
		{
			// Fill buffer with default char to tell master command is not supported/recognized
			memset(rx_buffer, 0xFF, TWIS_MAX_LENGHT);
			rx_length = TWIS_MAX_LENGHT
		}
		break;
	case TWIS_EVT_WRITE_REQ:
		if (p_event->data.buf_req)
		{
			nrf_drv_twis_rx_prepare(&m_twis, rx_buffer, rx_length);
		}
		break;
	case TWIS_EVT_WRITE_DONE:
		// Clear buffer
		memset(rx_buffer, 0x00, TWIS_MAX_LENGHT);
		break;

	case TWIS_EVT_READ_ERROR:
	case TWIS_EVT_WRITE_ERROR:
	case TWIS_EVT_GENERAL_ERROR:
		m_error_flag = true;
		break;
		default:
		break;
	}
}

RE: How to get command/data on I2C Slave, which has been send from I2C master.

pradeep8892 — Mon, 27 Apr 2020 16:04:55 GMT

Hi Jorgen,

May you please confirm, is the following implementation correct

uint8_t buffer[20] = {0};
int i = 0;
int j = 0;
static void twis_event_handler(nrf_drv_twis_evt_t const * const p_event)
{
debug_printf(" \nevent handler");
switch (p_event->type)
{
case TWIS_EVT_READ_REQ:
if (p_event->data.buf_req)
{
buffer[i] = p_event->data.rx_amount;
i++;
}
break;
case TWIS_EVT_READ_DONE:
i = 0;
break;
case TWIS_EVT_WRITE_REQ:
if (p_event->data.buf_req)
{

buffer[j] = p_event->data.tx_amount;
j++;
break;
}
break;
case TWIS_EVT_WRITE_DONE:
j = 0;
break;

case TWIS_EVT_READ_ERROR:
case TWIS_EVT_WRITE_ERROR:
case TWIS_EVT_GENERAL_ERROR:
m_error_flag = true;
break;
default:
break;
}
}

RE: How to get command/data on I2C Slave, which has been send from I2C master.

Jørgen Holmefjord — Mon, 27 Apr 2020 13:30:47 GMT

You define the receive buffers in the application, so it should be easy to keep track of what buffer is used, either a global buffer for all transfers or separate buffers along with a variable indicating which buffer is currently in use. You can then access this buffer directly in the WRITE_DONE event. The valid bytes in the buffer is indicated by the p_event->data.rx_amount variable.

RE: How to get command/data on I2C Slave, which has been send from I2C master.

pradeep8892 — Mon, 27 Apr 2020 13:12:50 GMT

Hi Jargen,

I understood your point. But how can i receive and store the data. May you please share some code to fetch that data/command in TWIS_EVT_READ/WRITE_DONE, it would great help.

Thanks & Regards,

Pradeep

RE: How to get command/data on I2C Slave, which has been send from I2C master.

Jørgen Holmefjord — Mon, 27 Apr 2020 12:42:46 GMT

Hi,

You will receive events in the twis_event_handler both when a read/write is requested (TWIS_EVT_READ/WRITE_REQ) and when it is done (TWIS_EVT_READ/WRITE_DONE). When the TWI master is done writing the command, you can check the received command in the WRITE_DONE event and prepare the TX buffer with the appropriate response. When the TWI master starts the read operation, you can provide the buffer in the READ_REQ event.

Best regards,
Jørgen