Only Sending 1 Byte

[aplatts]

Hi

Hopefully a quick question. I want to send a set of bytes 'shtpData' between to routines but only one byte is being sent:

Sending 'unit8_t *dataPacket' of 5 bytes.

bool sendPacket(uint8_t channelNumber, uint8_t dataLength, uint8_t *dataPacket)
{

	uint8_t shtpData[MAX_PACKET_SIZE];

	shtpData[0] = dataLength & 0xFF;
	shtpData[1] = dataLength >> 8;
	shtpData[2] = channelNumber;
	shtpData[3] = sequenceNumber[channelNumber]++;
	for (uint8_t i = 0; i < dataLength; i++) {shtpData[i+4] = dataPacket[i];}

	ret_code_t err_code = srm_nrfx_twi_tx(shtpData, dataLength + 4);
	if (err_code != NRF_SUCCESS) {return false;}

	return true;

}

Receiver 'pData' is only the first byte.

uint32_t srm_nrfx_twi_tx (uint8_t *pData, uint32_t len)
{

	ret_code_t err_code;

	nrfx_twi_xfer_desc_t xfer_init;
    xfer_init.type = NRFX_TWI_XFER_TX;
    xfer_init.address = BNO080_ADDR_SH2_0;
    xfer_init.primary_length = len;
    xfer_init.p_primary_buf = pData;

    err_code = nrfx_twi_xfer(&m_twi, &xfer_init, 0);
    if(err_code != NRF_SUCCESS){return err_code;}

	return NRF_SUCCESS;
}

Any ideas?

[Jørgen Holmefjord]

Hi,

What is BNO080_ADDR_SH2_0 defined as? Note that the address parameter should be set to the I2C address of the sensor, not the register you want to write to. The register address should normally be included in the tx_buffer.

Best regards,
Jørgen

[aplatts]

Hi the BNO-080 Address is - 

#define BNO080_ADDR_SH2_0 0x4A //default

Give me 48hrs, I have a new I2C analyser being delivered which I hope will shed some light on the issue. Let me get that in place and see what the actual traffic is on the I2C bus.

Please bare with me.

[aplatts]

Hi Jorgen

Having an I2C Analyser has solved many issues! I have one question I need help with.

With 'nrfx_twi_xfer' what is the largest buffer size which can be read (value set by primary_length within nrfx_twi_xfer_desc_t)?

Thanks

Andrew

[Jørgen Holmefjord]

Technically, you can set this to the maximum size of the data type (size_t = unsigned int = uint32_t = 2^32 - 1 = 4294967295), but you will run out of memory long before that. The TWI peripheral that nrfx_twi runs on does only send one byte at a time, the application needs to provide a new pointer for every byte being transferred. The buffer part is only used in software for the driver to handle this for you.

If you were to use the TWIM peripheral with nrfx_twim, there is a limitation of 65534 bytes for each transfer in nRF52840 (16-bit MAXCNT register), while it is limited to 255 bytes (8-bit MAXCNT register) on nRF52832.