How to talk to this A/D Converter in Linux (ADS7138)

For a project I'm thinking of using this relatively new IC from TI - the ADS7138. The issue (I believe, though I may be wrong) is that there is no driver for this chip in the kernel. Does anyone have any suggestions for a work around to talking to this driver? Is there another driver I could use or am I stuck writing a custom driver specific for this IC?

2 Answers

I've worked on a board bring-up project with the same IC. I couldn't find a driver for it so I wrote one myself. I hope it works for you as well:ADS7138 Driver

Till you find a compatible kernel driver or develop one yourself, you can quickly experiment with the ADC from user space using the i2c-tools. You can use either the command line tools or use the API to write your own app, but be cautious if you use the command line tools like i2cget(8), first read the man pages and pay attention to the warning section.

To use the API, open(2) the i2c device, set the slave address with ioctl(2), then use smbus APIs like i2c_smbus_write_word_data(), i2c_smbus_read_word_data() etc. You may take a look at the tools code like i2cget.c itself to see how the API is used. Following is a simple code to read a register from an I²C chip connected to /dev/i2c-0.

int fd = open("/dev/i2c-0", O_RDWR);
ioctl(fd, I2C_SLAVE, slave_address);
__s32 res = i2c_smbus_read_word_data(fd, register_address);
close(fd);

See kernel documentation or the web about i2c/smbus and instantiating i2c devices for more details.