how to install ADF5355 linux driver on Raspberry pi3 ?

Question

Hi all, 
 I'm not seeing ADF5355 driver in Raspberry pi kernel ( https://github.com/raspberrypi/linux ). I tried versions up to 4.16. 
 Under Synthesizers DDS/PLL category, I can see only ADF4350/ ADF4350 as shown below : 
 
 Also, ADF5355 IIO Wideband Synthesizer Linux Driver [Analog Devices Wiki] suggests to set the following options. 
 --- Industrial I/O support -*- Enable ring buffer support within IIO -*- Industrial I/O lock free software ring -*- Enable triggered sampling support 
 but what I get is as follows : There's no option for "Enable ring buffer support" & "Industrial I/O lock free software ring" 
 
 I saw this post : Stuck setting up ADF5355 and it says ADF5355 is working with Raspberry Pi3, but the post does not tell the steps taken to install the driver. I don't know much about kernel/driver installation & I don't know where to put .dts files, where to put source files (.h .c) etc. when adding new drivers. 
 Please bare with me, my linux kernel/driver installation knowledge is very limited. 
 It would be great if someone could guide me to control ADF5355 with RPi 3 using iio device driver. 
 Cheers,

ADIApproved · Accepted Answer

Are you building the driver as a kmod [the M option in menuconfig] or as a built-in into the kernel directly [ the star * option ] ? 
 As a kmod [kernel module] you have to make sure it auto-loads on boot. 
 As a built-in into the kernel it should always be available. 
 I think the chmod you are doing is a work-around for the fact that typically most sysfs files [the files under /sys] are accessible to the root user, and usually not accessible to normal users [the "pi" user]. 
 That's normal, since it's a security mechanism of the kernel. 
 chmod 777 makes it generally available to everybody; which [depending on the case] could be a security risk. 
 Technically, if you do "sudo echo 2512345678 > out_altvoltage0_frequency" it should also work directly. 
 For most services that run on Linux, this works by doing privilege separation: some parts are running as a user with elevated privileges, and talks to a client that has limited privileges/access via a limited set of rules/protocols. 
 You can use libiio to do this; iiod runs in the background with elevated privileges [and access to /sys/bus/iio] and libiio clients talk to iiod.)

ADIApproved · Answer

Hey, To make sure [and I'm sorry if this is redundant stuff] ; did you ? * copy the overlay file [dtbo] to your raspberry Pi's boot partition under /boot/overlays * add an entry in the /boot/config.txt file with dtoverlay=> /boot/config.txt ; fi ; reboot" You run it like (example): 192.168.1.10 adf5335 /home/user/dtc/dtc Arguments are: * IP address of the Pi ; you need to be able to SSH via the root user * device-tree overlay file [local file on your computer] ; has to be named adf5335.dts [in the above example] * device-tree compiler [on your computer; preferably full path] ; note that this has to be a fairly recent version that supports device-tree overlays ; I think that if you use this one, it should be ok: dtc/dtc.git - The Device Tree Compiler

ADIApproved · Answer

There's a small inconsistency between the filenames; so to make sure: 
 
 In your /boot/config.txt you added dtoverlay=adf5355 
 But your file seems to be named adf5355-overlay.dts 
 Question: did you copy adf5355 .dtbo or adf5355-overlay.dtbo in /boot/overlays ? ; because you may need to add dtoverlay=adf5355-overlay to make it work [if you copied adf5355-overlay.dts in /boot/overlays ]

ADIApproved · Answer

Sorry for omitting the pin-out stuff. 
 Michael could correct me here [if I'm wrong]. 
 But from the datasheet, it does not look like the chip can read data via SPI; the driver also doesn't seem to do any reads, just writes. 
 See http://www.analog.com/media/en/technical-documentation/data-sheets/ADF5355.pdf 
 
 page 7 shows how to write to the chip 
 page 9 explains each pin 
 
 So, 
 
 CLK ---------------> GPIO 11 (BCM 11) - SPI SCLK == correct 
 DATA ---------------> GPIO 9 (BCM 9) - SPI MISO == incorrect ; 
 
 should be DATA ---------------> GPIO 10 (BCM 10) - SPI MOS I - since you can only write to the chip 
 
 LE ---------------> GPIO 10 (BCM 10) - SPI MOSI == this also looks incorrect; according to the write timing diagram [page 7], this behaves more like an SPI CS0 ; I admit, the name is misleading for CE ; 
 
 so, this should be LE ---------------> GPIO 8 (BCM 8) - SPI CS0 
 
 CE ---------------> GPIO 8 (BCM 8) - SPI CS0 == this looks incorrect too; since this chip enable controls whether the pin is powered up or not; I suggest you tie this Pin 0 which outputs 3.3V [or any pin on the RPi GPIO pinout that outputs a constant voltage]; there doesn't seem to be a Max limit for the logic high voltages [on page 4] 
 
 Thanks 
 Alex

mhennerich · Answer

Correct ADF5355 and similar are write only. LE functions as a typical SPI CS, while chip CE can be tied to Vdd. 
 -Michael

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how to install ADF5355 linux driver on Raspberry pi3 ?