ADF4350
ADF4350 IIO Wideband Synthesizer Linux Driver.
Supported Devices
Evaluation Boards
Reference Circuits
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 |
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driver |
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include |
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Documentation |
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Documentation |
Adding Linux driver support
Kernel configuration
Configure kernel with make menuconfig (alternatively use make xconfig or
make qconfig)
Note
The ADF4350 Driver depends on CONFIG_SPI
Linux Kernel Configuration
Device Drivers --->
<*> Industrial I/O support --->
--- Industrial I/O support
-*- Enable buffer support within IIO
-*- Enable triggered sampling support
*** Phase-Locked Loop (PLL) frequency synthesizers ***
[--snip--]
<*> Analog Devices ADF4350/ADF4351 Wideband Synthesizers
[--snip--]
Devicetree configuration
Required properties:
- compatible: Should be one of
* "adi,adf4350": When using the ADF4350 device
* "adi,adf4351": When using the ADF4351 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
ADF435x 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.
- adi,channel-spacing: Channel spacing in Hz (influences MODULUS).
- 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,phase-detector-polarity-positive-enable: Enables positive phase
detector polarity. Default = negative.
- adi,lock-detect-precision-6ns-enable: Enables 6ns lock detect precision.
Default = 10ns.
- adi,lock-detect-function-integer-n-enable: Enables lock detect
for integer-N mode. Default = factional-N mode.
- adi,charge-pump-current: Charge pump current in microamps.
Default = 2500 microamps (2.5 mA).
- 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,low-spur-mode-enable: Enables low spur mode.
Default = Low noise mode.
- adi,cycle-slip-reduction-enable: Enables cycle slip reduction.
- adi,charge-cancellation-enable: Enabled charge pump
charge cancellation for integer-N modes.
- adi,anti-backlash-3ns-enable: Enables 3ns antibacklash pulse width
for integer-N modes.
- adi,band-select-clock-mode-high-enable: Enables faster band
selection logic.
- adi,12bit-clk-divider: Clock divider value used when
adi,clk-divider-mode != 0
- adi,clk-divider-mode:
Valid values for the clkdiv mode are:
0: Clock divider off (default)
1: Fast lock enable
2: Phase resync enable
- adi,aux-output-enable: Enables auxiliary RF output.
- adi,aux-output-fundamental-enable: Selects fundamental VCO output on
the auxiliary RF output. Default = Output of RF dividers.
- adi,mute-till-lock-enable: Enables Mute-Till-Lock-Detect function.
- adi,output-power: Output power selection.
Valid values for the power mode are:
0: -4dBm (default)
1: -1dBm
2: +2dBm
3: +5dBm
- adi,aux-output-power: Auxiliary output power selection.
Valid values for the power mode are:
0: -4dBm (default)
1: -1dBm
2: +2dBm
3: +5dBm
Example:
lo_pll0_rx_adf4351: adf4351-rx-lpc@4 {
compatible = "adi,adf4351";
reg = <4>;
spi-max-frequency = <10000000>;
clocks = <&clk0_ad9523 9>;
clock-names = "clkin";
adi,channel-spacing = <10000>;
adi,power-up-frequency = <2400000000>;
adi,phase-detector-polarity-positive-enable;
adi,charge-pump-current = <2500>;
adi,output-power = <3>;
adi,mute-till-lock-enable;
};
Platform-data configuration
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 adf4350_platform_data - platform specific information
* @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.
* @r2_user_settings: User defined settings for ADF4350/1 REGISTER_2.
* @r3_user_settings: User defined settings for ADF4350/1 REGISTER_3.
* @r4_user_settings: User defined settings for ADF4350/1 REGISTER_4.
* @gpio_lock_detect: Optional, if set with a valid GPIO number,
* a PLL_LOCKED device attribute is created.
* If not used - set to -1.
*/
struct adf4350_platform_data {
unsigned long clkin;
unsigned long channel_spacing;
unsigned long long power_up_frequency;
unsigned short ref_div_factor; /* 10-bit R counter */
bool ref_doubler_en;
bool ref_div2_en;
unsigned r2_user_settings;
unsigned r3_user_settings;
unsigned r4_user_settings;
int gpio_lock_detect;
};
static struct adf4350_platform_data adf4351_pdata = {
.clkin = 10000000,
.channel_spacing = 10000,
.r2_user_settings = ADF4350_REG2_PD_POLARITY_POS |
ADF4350_REG2_CHARGE_PUMP_CURR_uA(2500),
.r3_user_settings = ADF4350_REG3_12BIT_CLKDIV_MODE(0),
.r4_user_settings = ADF4350_REG4_OUTPUT_PWR(0) |
ADF4350_REG4_MUTE_TILL_LOCK_EN,
.gpio_lock_detect = -1,
};
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
Depending on the DDS IC used, you may need to set the modalias accordingly, matching your part name. It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.
static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_ADF4350) || defined(CONFIG_ADF4350_MODULE)
{
.modalias = "adf4350",
.max_speed_hz = 1000000, /* max spi clock (SCK) speed in HZ */
.bus_num = 0,
.chip_select = GPIO_PF10 + MAX_CTRL_CS, /* GPIO controlled SSEL */
.platform_data = NULL, /* No spi_driver specific config */
.mode = SPI_MODE_0,
},
#endif
};
static int __init board_init(void)
{
[--snip--]
spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));
[--snip--]
return 0;
}
arch_initcall(board_init);
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:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
iio:device0
root:/sys/bus/iio/devices> iio:device0
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> ls -l
-r--r--r-- 1 root root 4096 Jan 1 00:01 dev
-r--r--r-- 1 root root 4096 Jan 1 00:01 name
-rw-r--r-- 1 root root 4096 Jan 1 00:01 out_altvoltage0_frequency
-rw-r--r-- 1 root root 4096 Jan 1 00:01 out_altvoltage0_frequency_resolution
-rw-r--r-- 1 root root 4096 Jan 1 00:01 out_altvoltage0_powerdown
-rw-r--r-- 1 root root 4096 Jan 1 00:01 out_altvoltage0_refin_frequency
drwxr-xr-x 2 root root 0 Jan 1 00:01 power
lrwxrwxrwx 1 root root 0 Jan 1 00:01 subsystem -> ../../../../../bus/iio
-rw-r--r-- 1 root root 4096 Jan 1 00:01 uevent
Identify the device
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat name
adf4350
Set Output Frequency
/sys/bus/iio/devices/iio:deviceX/out_altvoltage0_frequency
Stores the PLL frequency in Hz. Reading returns the actual frequency in Hz. After a frequency change, allow time for the PLL to lock. If a lock-detect GPIO is configured, the frequency read returns EBUSY while the PLL is unlocked.
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 144825000 > out_altvoltage0_frequency
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltage0_frequency
144825000
Set frequency resolution/channel spacing
/sys/bus/iio/devices/iio:deviceX/out_altvoltage0_frequency_resolution
Stores PLL Y frequency resolution/channel spacing in Hz. The value given directly influences the MODULUS used by the fractional-N PLL. It is assumed that the algorithm that is used to compute the various dividers, is able to generate proper values for multiples of channel spacing.
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 10000 > out_altvoltage0_frequency_resolution
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltage0_frequency_resolution
10000
Set reference frequency
/sys/bus/iio/devices/iio:deviceX/out_altvoltage0_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 write updates the reference clock (when supplied through the clock framework) and immediately retunes the PLL to the previously requested output frequency. Use channel 0 in the commands below.
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 10000000 > out_altvoltage0_refin_frequency
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltage0_frequency_resolution
10000000
Enable Power-Down
/sys/bus/iio/devices/iio:deviceX/out_altvoltage0_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:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> echo 1 > out_altvoltage0_powerdown
root:/sys/devices/platform/bfin-spi.0/spi0.18/iio:device0> cat out_altvoltage0_powerdown
1
Query Lock Detect
When a lock-detect GPIO is configured, read out_altvoltage0_frequency to
check whether the PLL has locked: the read fails with EBUSY while unlocked.
Without that GPIO, the read does not reflect the lock status.