AD4000 driver
Device driver for Analog Devices Inc. AD4000 series of ADCs.
Supported devices
Wiring connections
Devices of the AD4000 series can be connected to the SPI host controller in a few different modes.
CS mode, 3-wire turbo mode
Datasheet “3-wire” mode is what most resembles standard SPI connection which,
for these devices, comprises of connecting the controller CS line to device CNV
pin and other SPI lines as usual. This configuration is (misleadingly) called
“CS Mode, 3-Wire Turbo Mode” connection in datasheets.
NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
same of standard spi-3wire mode.
This is the only connection mode that allows configuration register access but
it requires the SPI controller to support the SPI_MOSI_IDLE_HIGH feature.
Omit the adi,sdi-pin property in device tree to select this mode.
+-------------+
+ ----------------------------------| SDO |
| | |
| +-------------------| CS |
| v | |
| +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
CS mode, 3-wire, without busy indicator
Another wiring configuration supported as “3-wire” mode has the SDI pin
hard-wired to digital input/output interface supply (VIO). In this setup, the
controller is not required to support SPI_MOSI_IDLE_HIGH but register access
is not possible. This connection mode saves one wire and works with any SPI
controller.
Set the adi,sdi-pin device tree property to "high" to select this mode.
+-------------+
+--------------------| CS |
v | |
VIO +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
Alternatively, a GPIO may be connected to the device CNV pin. This is similar to the previous wiring configuration but saves the use of a CS line.
+-------------+
+--------------------| GPIO |
v | |
VIO +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+
CS mode, 4-wire without busy indicator
In datasheet “4-wire” mode, the controller CS line is connected to the ADC SDI pin and a GPIO is connected to the ADC CNV pin. This connection mode may better suit scenarios where multiple ADCs can share one CNV trigger.
Set adi,sdi-pin to "cs" to select this mode.
+-------------+
+ ----------------------------------| CS |
| | |
| +-------------------| GPIO |
| v | |
| +--------------------+ | HOST |
| | CNV | | |
+--->| SDI AD4000 SDO |-------->| SDI |
| SCK | | |
+--------------------+ | |
^ | |
+--------------------| SCLK |
+-------------+