ADF5355
ADF5355 IIO Wideband Synthesizer Linux Driver.
Supported Devices
Reference Circuits
Evaluation Boards
Description
This is a Linux industrial I/O (Linux Industrial I/O Subsystem) subsystem driver, targeting serial interface PLL Synthesizers. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See Linux Industrial I/O Subsystem for more information.
Source Code
Status
Files
Function |
File |
|---|---|
driver |
|
include |
|
Documentation |
master?Documentation/devicetree/bindings/iio/frequency/adf5355.txt |
Example platform device initialization
For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.
For devices on custom boards, as typical of embedded and SoC-(system-on-chip)
based hardware, Linux uses platform_data to point to board-specific structures
describing devices and how they are connected to the SoC. This can include
available ports, chip variants, preferred modes, default initialization,
additional pin roles, and so on. This shrinks the board-support packages (BSPs)
and minimizes board and application specific #ifdefs in drivers.
The reference frequency and GPIO numbers may vary between boards. The
platform_data for the device’s struct device holds this information.
/**
* struct adf5355_platform_data - platform specific information
* @name: Optional device name.
* @clkin: REFin frequency in Hz.
* @channel_spacing: Channel spacing in Hz (influences MODULUS).
* @power_up_frequency: Optional, If set in Hz the PLL tunes to the desired
* frequency on probe.
* @ref_div_factor: Optional, if set the driver skips dynamic calculation
* and uses this default value instead.
* @ref_doubler_en: Enables reference doubler.
* @ref_div2_en: Enables reference divider.
* @gpio_lock_detect: Optional, if set with a valid GPIO number,
* pll lock state is tested upon read.
* If not used - set to -1.
* @outa_en: Enables or disables the primary RF output
* @outb_en: Enables or disables the auxiliary/high RF output
* @outa_power Set the value of the primary RF output power level
* @outb_power Set the value of the auxiliary/high RF output power level
* @mute_till_lock_detect_en: If enabled, the supply current to the RF
output stage is shut down until the device achieves lock,
as determined by the digital lock detect circuitry.
* @phase_detector_polarity_neg: When a passive loop filter or a noninverting
* active loop filter is used, set to positive.
* If an active filter with an inverting characteristic is
* used, set this to negative.
* @cp_neg_bleed_en: Use of constant negative bleed. (recommended for most
* fractional-N applications)
* @cp_gated_bleed_en: Enables gated bleed.
* @cp_curr_uA: Set the charge pump current in uA. Set this value to
* the charge pump current that the loop
* filter is designed with. For the lowest spurs, the
* 0.9 mA setting is recommended.
* @mux_out_sel: Controls the on-chip multiplexer (MUXOUT).
* @mux_out_3V3_en: MUXOUT is programmable to two logic levels. Clear this to
* select 1.8 V logic, and set it to select 3.3 V logic.
*
*/
struct adf5355_platform_data {
char name[32];
unsigned long clkin;
unsigned long long power_up_frequency;
u32 ref_div_factor; /* 10-bit R counter */
bool ref_diff_en;
bool ref_doubler_en;
bool ref_div2_en;
bool mux_out_3V3_en; /* otherwise 1V8 */
u32 mux_out_sel;
u32 cp_curr_uA;
bool cp_neg_bleed_en;
bool cp_gated_bleed_en;
bool phase_detector_polarity_neg;
bool mute_till_lock_detect_en;
bool outb_en;
bool outa_en;
u32 outb_power;
u32 outa_power;
int gpio_lock_detect;
};
Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.
This method is appropriate when the SPI bus is a system bus, as in many
embedded systems, wherein each SPI bus has a number which is known in advance.
It is thus possible to pre-declare the SPI devices that inhabit this bus. This
is done with an array of struct spi_board_info, which is registered by
calling spi_register_board_info().
For more information see: Overview of Linux kernel SPI support
Devicetree bindings
Required properties:
- compatible: Should be one of
* "adi,adf5355": When using the ADF5355 device
* "adi,adf5356": When using the ADF5356 device
* "adi,adf4355": When using the ADF4355 device
* "adi,adf4355-2": When using the ADF4355-2 device
* "adi,adf4355-3": When using the ADF4355-3 device
- reg: SPI chip select numbert for the device
- spi-max-frequency: Max SPI frequency to use (< 20000000)
- clocks: From common clock binding. Clock is phandle to clock for
ADF5355 Reference Clock (CLKIN).
Optional properties:
- gpios: GPIO Lock detect - If set with a valid phandle and GPIO
number, pll lock state is tested upon read.
- clock-output-names : From common clock binding to override the
default output clock name.
- adi,power-up-frequency: If set in Hz the PLL tunes to
the desired frequency on probe.
- adi,reference-div-factor: If set the driver skips dynamic calculation
and uses this default value instead.
- adi,reference-doubler-enable: Enables reference doubler.
- adi,reference-div2-enable: Enables reference divider.
- adi,reference-differential-input-enable: The device permits use of
either differential or single ended reference sources.
For differential sources set this property.
- adi,phase-detector-polarity-negative-enable: When a passive loop
filter or a noninverting active loop filter is used,
clear for positive. If an active filter with an
inverting characteristic is used, set this to negative.
- adi,charge-pump-current: Set the charge pump current in uA.
Set this value to the charge pump current that the loop
filter is designed with. For the lowest spurs, the
900 uA setting is recommended.
- adi,charge-pump-negative-bleed-enable: Use of constant negative bleed.
(recommended for most fractional-N applications)
- adi,charge-pump-gated-bleed-enable: Enables gated bleed.
- adi,muxout-select: On chip multiplexer output selection.
Valid values for the multiplexer output are:
0: Three-State Output (default)
1: DVDD
2: DGND
3: R-Counter output
4: N-Divider output
5: Analog lock detect
6: Digital lock detect
- adi,muxout-level-3v3-enable: MUXOUT is programmable to two logic
levels. Clear this to select 1.8 V logic,
and set it to select 3.3 V logic.
- adi,mute-till-lock-enable: If enabled, the supply current to the RF
output stage is shut down until the device achieves lock,
as determined by the digital lock detect circuitry.
- adi,output-b-enable: Enables or disables the primary RF output
- adi,output-a-enable: Enables or disables the auxiliary/high RF output
- adi,output-a-power: Primary RF output power selection.
Valid values for the power mode are:
0: -4dBm (default)
1: -1dBm
2: +2dBm
3: +5dBm
- adi,output-b-power: Auxiliary output power selection.
Valid values for the power mode are:
0: -4dBm (default)
1: -1dBm
2: +2dBm
3: +5dBm
Example:
&spi0 {
status = "okay";
adf5355@0 {
compatible = "adf5355";
reg = <0>;
spi-max-frequency = <1000000>;
clocks = <&adf4351_clkin>;
clock-names = "clkin";
clock-output-names = "adf5355_out";
adi,charge-pump-current = <900>;
adi,muxout-select = <6>;
adi,mute-till-lock-enable;
adi,output-a-power = <2>;
adi,output-b-power = <2>;
adi,output-b-enable;
adi,output-a-enable;
adi,charge-pump-negative-bleed-enable;
adi,reference-differential-input-enable;
adi,muxout-level-3v3-enable;
adi,power-up-frequency = /bits/ 64 <123000000>;
};
adf5356@1 {
#clock-cells = <0>;
compatible = "adi,adf5356";
reg = <1>;
spi-max-frequency = <1000000>;
clocks = <&ad9361_clkin>;
clock-names = "clkin";
clock-output-names = "ADF5356";
adi,charge-pump-current = <900>;
adi,muxout-select = <6>;
adi,muxout-level-3v3-enable;
adi,mute-till-lock-enable;
adi,output-a-power = <3>;
adi,output-b-power = <0>;
adi,charge-pump-negative-bleed-enable;
adi,reference-differential-input-enable;
adi,power-up-frequency = /bits/ 64 <1500000000>;
adi,output-a-enable;
adi,clock-shift = <2>;
adi,reference-div2-enable;
adi,reference-div-factor = <1>;
};
};
Adding Linux driver support
Configure kernel with make menuconfig (alternatively use make xconfig or
make qconfig)
Note
The ADF5355 Driver depends on CONFIG_SPI
Linux Kernel Configuration
Device Drivers --->
<*> Industrial I/O support --->
--- Industrial I/O support
-*- Enable ring buffer support within IIO
-*- Industrial I/O lock free software ring
-*- Enable triggered sampling support
*** Phase-Locked Loop (PLL) frequency synthesizers ***
[--snip--]
<*> Analog Devices ADF5355/ADF4355 Wideband Synthesizers
[--snip--]
Hardware configuration
Driver testing
Each and every IIO device, typically a hardware chip, has a device folder under
/sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under
every of these directory folders reside a set of files, depending on the
characteristics and features of the hardware device in question. These files
are consistently generalized and documented in the IIO ABI documentation. In
order to determine which IIO deviceX corresponds to which hardware device, the
user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case
the sequence in which the iio device drivers are loaded/registered is constant,
the numbering is constant and may be known in advance.
root@linaro-ubuntu-desktop:~# cd /sys/bus/iio/devices
root@linaro-ubuntu-desktop:/sys/bus/iio/devices#
root@linaro-ubuntu-desktop:/sys/bus/iio/devices# ls
iio:device0 iio:device1
root@linaro-ubuntu-desktop:/sys/bus/iio/devices# cd iio\:device1
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# ls -al
total 0
drwxr-xr-x 3 root root 0 Jan 1 00:00 .
drwxr-xr-x 4 root root 0 Jan 1 00:00 ..
-rw-rw-rw- 1 root root 4096 Jan 1 00:00 dev
-rw-rw-rw- 1 root root 4096 Jan 1 00:00 name
-rw-rw-rw- 1 root root 4096 Jan 1 00:02 out_altvoltage0_frequency
-rw-rw-rw- 1 root root 4096 Jan 1 00:01 out_altvoltage0_powerdown
-rw-rw-rw- 1 root root 4096 Jan 1 00:00 out_altvoltage1_frequency
-rw-rw-rw- 1 root root 4096 Jan 1 00:01 out_altvoltage1_powerdown
-rw-rw-rw- 1 root root 4096 Jan 1 00:00 out_altvoltage_refin_frequency
drwxrwxrwx 2 root root 0 Jan 1 00:00 power
lrwxrwxrwx 1 root root 0 Jan 1 00:00 subsystem -> ../../../../../../../../bus/iio
-rw-rw-rw- 1 root root 4096 Jan 1 00:00 uevent
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1#
Show device name
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# cat name
adf5355
Set Output Frequency
/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_frequency
Stores PLL Y frequency in Hz. Reading returns the actual frequency in Hz.
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# echo 2512345678 > out_altvoltage0_frequency
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# cat out_altvoltage0_frequency
2512345678
Set reference frequency
/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_refin_frequency
Sets PLL Y REFin frequency in Hz. In some clock chained applications, the reference frequency used by the PLL may change during runtime. This attribute allows the user to adjust the reference frequency accordingly. The value written has no effect until out_altvoltageY_freq is updated.
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# cat out_altvoltage_refin_frequency
122880000
Enable Power-Down
/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_powerdown
If available, this attribute allows the user to power down the PLL and it’s RFOut buffers. This is in particular useful during REFin changes.
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# echo 1 > out_altvoltage0_powerdown
root@linaro-ubuntu-desktop:/sys/bus/iio/devices/iio:device1# cat out_altvoltage0_powerdown
1