This contains the generic SPI driver and the LTC2414/LTC2418 SPI ADC chip using the SPI API. main.c is the test program to implement the ADC read to-the-go.
In my case, I am using Armbian Debian Linux. According to the Official Documentation, SPI1 with a specific CS select pin 0 and SPI frequency is overlayed to the original device tree. You can then find /dev/spidev1.0 file after the reboot.
The provided Linux kernel headers contain SPI API: linux/spi/spidev.h. You can find it under /usr/include/linux/spi/spidev.
To manipulate the SPIdev device /dev/spidev1.0, the system IOCTL API is used. The include is sys/ioctl.h.
The API contains the init function with a config struct, read, write and sync functions with continuous packet number parameter.
This uses the spi.h API provided as the SPIdev backend.
In order to change the ADC chip between LTC2414 and LTC2418, change the line in ltc241x.h as either of the following:
#define LTC241x LTC2414 // For LTC2414
#define LTC241x LTC2418 // For LTC2418
There are init, offset calibration and read functions defined.
Please noted that there is maximum 166ms conversion time with the internal oscillator accordint to the datasheet, the time interval between two reads should be at lease 170ms. It is also observed that too fast reading can make the result inaccurate so at least 300ms time interval between two reads is suggested.
To build the program, run make. Clean the solution with make clean.
(Optional, make debug to build the debug version for gdb. make verbose to build the debug version with more detailed prints to stdout.)
To run the program, run ./main.
- Init the SPIdev bus for LTC2418.
- Calibrate the offset of all analogue channels.
- Read channel n.
- Sleep for 500ms.
- Repeat Step 3.
The MIT License (MIT)
Copyright © 2022 Xiaosheng An
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