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I'm trying to read/write to a FM24CL64-GTR FRAM chip that is connected over a I2C bus on address 0b 1010 011 . When I'm trying to write 3 bytes (data address 2 bytes, + data one byte), I get a kernel message ( [12406.360000] i2c-adapter i2c-0: sendbytes: NAK bailout. ), as well as the write returns != 3. See code below: #include <linux/i2c-dev.h> #include <fcntl.h> #include <unistd.h> #include <stdint.h> int file; char filename[20]; int addr = 0x53; // 0b1010011; /* The I2C address */ uint16_t dataAddr = 0x1234; uint8_t val = 0x5c; uint8_t buf[3]; sprintf(filename,"/dev/i2c-%d",0); if ((file = open(filename,O_RDWR)) < 0) exit(1); if (ioctl(file,I2C_SLAVE,addr) < 0) exit(2); buf[0] = dataAddr >> 8; buf[1] = dataAddr & 0xff; buf[2] = val; if (write(file, buf, 3) != 3) exit(3); ... However when I write 2 bytes, then write another byte, I get no kernel error, but when trying to read from the FRAM, I always get back 0. Here is the code to read from the FRAM: uint8_t val; if ((file = open(filename,O_RDWR)) < 0) exit(1); if (ioctl(file,I2C_SLAVE,addr) < 0) exit(2); if (write(file, &dataAddr, 2) != 2) { exit(3); if (read(file, &val, 1) != 1) { exit(3); None of the functions return an error value, and I have also tried it with: #include <linux/i2c.h> struct i2c_rdwr_ioctl_data work_queue; struct i2c_msg msg[2]; uint8_t ret; work_queue.nmsgs = 2; work_queue.msgs = msg; work_queue.msgs[0].addr = addr; work_queue.msgs[0].len = 2; work_queue.msgs[0].flags = 0; work_queue.msgs[0].buf = &dataAddr; work_queue.msgs[1].addr = addr; work_queue.msgs[1].len = 1; work_queue.msgs[1].flags = I2C_M_RD; work_queue.msgs[1].buf = &ret; if (ioctl(file,I2C_RDWR,&work_queue) < 0) exit(3); Which also succeeds, but always returns

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