iio: impedance-analyzer: New driver for AD5933/4 Impedance Converter, Network Analyzer

The AD5933 is a high precision impedance converter system solution
that combines an on-board frequency generator with a 12-bit, 1 MSPS,
analog-to-digital converter (ADC). The frequency generator allows an
external complex impedance to be excited with a known frequency.

The response signal from the impedance is sampled by the on-board ADC
and a discrete Fourier transform (DFT) is processed by an on-chip DSP engine.
The DFT algorithm returns a real (R) and imaginary (I) data-word at each
output frequency.

Changes since V1:

Apply list review feedback:
Consistently use poll_time_jiffies.
Use be|le cpu endian helpers where applicable.
Add various comments.

Changes since V2:

Fix KernelVersion tag in Documentation.
Declare ad5933_default_pdata static.
Fix typos.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/Documentation/sysfs-bus-iio-impedance-analyzer-ad5933

+What:		/sys/bus/iio/devices/iio:deviceX/outY_freq_start
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Frequency sweep start frequency in Hz.
+
+What:		/sys/bus/iio/devices/iio:deviceX/outY_freq_increment
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Frequency increment in Hz (step size) between consecutive
+		frequency points along the sweep.
+
+What:		/sys/bus/iio/devices/iio:deviceX/outY_freq_points
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Number of frequency points (steps) in the frequency sweep.
+		This value, in conjunction with the outY_freq_start and the
+		outY_freq_increment, determines the frequency sweep range
+		for the sweep operation.
+
+What:		/sys/bus/iio/devices/iio:deviceX/outY_settling_cycles
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Number of output excitation cycles (settling time cycles)
+		that are allowed to pass through the unknown impedance,
+		after each frequency increment, and before the ADC is triggered
+		to perform a conversion sequence of the response signal.

drivers/staging/iio/Kconfig

@@ -62,6 +62,7 @@ source "drivers/staging/iio/addac/Kconfig"
 source "drivers/staging/iio/dac/Kconfig"
 source "drivers/staging/iio/dds/Kconfig"
 source "drivers/staging/iio/gyro/Kconfig"
+source "drivers/staging/iio/impedance-analyzer/Kconfig"
 source "drivers/staging/iio/imu/Kconfig"
 source "drivers/staging/iio/light/Kconfig"
 source "drivers/staging/iio/magnetometer/Kconfig"

drivers/staging/iio/Makefile

@@ -16,6 +16,7 @@ obj-y += addac/
 obj-y += dac/
 obj-y += dds/
 obj-y += gyro/
+obj-y += impedance-analyzer/
 obj-y += imu/
 obj-y += light/
 obj-y += magnetometer/

drivers/staging/iio/impedance-analyzer/Kconfig

+#
+# Impedance Converter, Network Analyzer drivers
+#
+comment "Network Analyzer, Impedance Converters"
+
+config AD5933
+	tristate "Analog Devices AD5933, AD5934 driver"
+	depends on I2C
+	select IIO_RING_BUFFER
+	select IIO_SW_RING
+	help
+	  Say yes here to build support for Analog Devices Impedance Converter,
+	  Network Analyzer, AD5933/4, provides direct access via sysfs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad5933.

drivers/staging/iio/impedance-analyzer/Makefile

+#
+# Makefile for Impedance Converter, Network Analyzer drivers
+#
+
+obj-$(CONFIG_AD5933) += ad5933.o

drivers/staging/iio/impedance-analyzer/ad5933.h

+/*
+ * AD5933 AD5934 Impedance Converter, Network Analyzer
+ *
+ * Copyright 2011 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#ifndef IIO_ADC_AD5933_H_
+#define IIO_ADC_AD5933_H_
+
+/*
+ * TODO: struct ad5933_platform_data needs to go into include/linux/iio
+ */
+
+/**
+ * struct ad5933_platform_data - platform specific data
+ * @ext_clk_Hz:		the external clock frequency in Hz, if not set
+ *			the driver uses the internal clock (16.776 MHz)
+ * @vref_mv:		the external reference voltage in millivolt
+ */
+
+struct ad5933_platform_data {
+	unsigned long			ext_clk_Hz;
+	unsigned short			vref_mv;
+};
+
+#endif /* IIO_ADC_AD5933_H_ */