Only Sending 1 Byte

RE: Only Sending 1 Byte

Jørgen Holmefjord — Tue, 12 May 2020 12:05:06 GMT

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.

RE: Only Sending 1 Byte

aplatts — Tue, 12 May 2020 10:32:49 GMT

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

RE: Only Sending 1 Byte

aplatts — Mon, 04 May 2020 12:13:20 GMT

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.

RE: Only Sending 1 Byte

Jørgen Holmefjord — Mon, 04 May 2020 12:02:33 GMT

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