Dave, As I recall, our I2C driver does not support block transfers. It is necessary to read (or write) one byte at a time. So you would have to loop from 0xAA-0xBF.
A long time ago I prepared patches for a small subset of our supported I2C controllers, but they (the patches) are long gone. Good luck! On Tue, 17 Aug 2021, Dave Tyson wrote:
I am trying to get data from a temperature/pressure sensor connected via i2c to a banana pi running NetBSD current. I understand the I2C protocol but I am having a bit of difficulty understanding what appears on the wire when the I2C_IOCTL_EXEC is called with the various op commands. By trial and error I seem to have been able to read the data, but want to check a few things in case I am doing it all wrong :-) The device appears at address 0x77 (it's a BMP085) with i2cscan, the data sheet indicates the read address=0xEF/write address=0xEE. I just put 0x77 in the address field and assume the read/write bit on the wire is added based on the op code (I2C_OP_WRITE, I2C_OP_READ etc). The device has R/O calibration data in 22 contiguous registers starting at 0xAA->0xBF. Linux programs seem to grab the data in one go starting at 0xAA. The other registers needed to initiate a sensor data grab are R/W - you write a control byte into the 0xF4 register, wait a bit and then read the data from another register set. A naive attempt to read the calibration data using: command = 0xAA ; iie.iie_op = I2C_OP_READ ; iie.iie_addr = 0x77 ; iie.iie_cmd = &command ; iie.iie_cmdlen = 1 ; iie.iie_buf = &caldata[0] ; iie.iie_buflen = 22; if ((ioctl(iicfd, I2C_IOCTL_EXEC, &iie)) !=0) { printf("read failed %d\n",errno) ; exit(1) ; } actually seemed to work OK, but I don't understand why! I had expected to need a I2C_OP_WRITE first followed by a I2C_OP_READ_STOP. The former would send a start bit, the device addr/write bit and the target register. The latter would send a (re)start bit, device addr/read bit, pull the data back and issue a stop. Maybe because the register I am addressing is R/O there is no need for a write and what I am doing is correct... (or do I need a I2C_OP_READ_STOP) Could someone explain what actually gets sent on the wire for the various ops: I2C_OP_READ I2C_OP_READ_WITH_STOP I2C_OP_WRITE I2C_OP_WRITE_WITH_STOP I2C_OP_READ_BLOCK I2C_OP_WRITE_BLOCK and what difference block operations make as man ICC(4) is terse to say the least. Cheers, Dave !DSPAM:611be3ce51591168618607!
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