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zram issue Sat Feb 22, 2025

Big thanks to forum user spina for finding this.
Tho not a game stopper, doesn't seem to affect the operation. Just entries into /var/log/boot.log
Is related to swap.
So far no reports of adverse behavior has been reported.

A reboot can be done now or you can edit the file mentioned below to prior to rebooting.

By default up to 4GB of ram or half the ram is used, depending on how much ram one has.

On my 4GB system I have the following entry, which allocates 1GB to zram swap......the file to edit is after the # symbol.
Apologies for missing this prior to releasing the images.

I wasn't thinking of putting it the connector shell but having a surface mount connector if they exist that plugs straight in like a raspberry pi hat.
The amphenol connector used by Hypertherm and Thermal Dynamics, I think comes with surface mount options....

Glad you like my idea, Pretty cool one I thought!

Thanks Rob. I'll get the 7C81 when it comes back in stock.

I thought that I saw somewhere that the 7C81 is now supported in the PNC config Wizard. I could easily be wrong though.

Thanks.

I was asked to post in this thread about a problem I encountered with installing the official LinuxCNC image for the Raspberry Pi 4b. 

The issue I had was once the image was burned to the SD and booted the monitor that I have for the RPi was skewed on the login screen. It looked like the picture below. You could make out what it was showing and could log in and it would take you to the desktop but it was also skewed. You could make out what was there and navigate to the display settings, change the resolution, and get it working, but the changes were not persistent. Everytime the RPi booted it would revert back to the skewed resolution.

It was suggested that the HDMI cable could be at fault, and this is a good suggestion. I did try a couple different HDMI cables with the same results. 

I tried a lot of things from internet searches about this problem, but nothing seemed to work, but I finally found a clue from one post in the internet that was hard to find. I wound up changing several things in the config.txt file in the top level directory of the SD card. I used a Windows laptop to make the changes. Once I had it working, I reversed the changes one by one to see which change was the one that actually fixed it. Here is what I found:

In config.txt you will find this section in there with notes about what I changed to fix it:
[pi4]
dtoverlay=vc4-kms-v3d,cma-512              Comment out this line
#dtoverlay=vc4-kms-v3d-pi4
#dtoverlay=vc4-fkms-v3d                          Uncomment this line
max_framebuffers=2
arm_boost=1
#disable_fw_kms_setup=1

As I understand it this forces the use of an older display driver.

I believe this problem was due to an incompatability between the display I was using (Cheap Chinese 10 display) and the newest driver on the RPi. Forcing it to use the older driver got it working perfectly.

BTW, I also tried the same SD card on my son's RPi 5 and had no problems even with the unmodified config.txt.

Incidentally, the display I was using is a cheap one I use as a second display when I travel for work. I bought cheap because it is likely to get busted up in luggage some day. For my final LinuxCNC display I will be using a different touch screen display. Hopefully that one will work well.

I hope this will be helpful to anyone who may encounter the same problem.

The 7c81 will be fine. The only issue the wizzard doesn't support the 7c81 but you can pick a 5i25 in the wizzard and edit the files after to suit, just replace 5i25 with 7c81 and change the loading of the driver to suit.

I actually made a "homemade clone" of a 7c81 using an FPGA board from Aliexpress and some custom boards. The only difficult part was modding the hostmot2 sources to suit. Pete from Mesa was helpful with this project and I'm very appreciative of the support he give on these projects. My reason for going this way is it was a cheaper option, freight to Australia almost doubles the price, and I was looking for a "challenge". BTW the same hardware will work with the Linuxcnc-RIO project, and with the addition on a Wiznet ethernet module it allows for an ethernet option with the Linuxcnc-RIO project but not with the standard hostmot2 firmware (that would require some work on the Linuxcnc side and the FPGA side)
github.com/ozzyrob/Linuxcnc-FPGA

When using software stepping the upper limit will depend on the base thread period you can work with on the RPi4.

All The Best
Rob

I have been reading a lot about options with the RPi and LinuxCNC, and am just getting more confused so I thought I would just ask a couple of hopefully simple questions.

I have a 3-axis (sometimes 4 axis) mill currently running LinuxCNC on an OrangePi. It has been run with GRBL on an arduino, and an old PC with LinuxCNC. The current setup works okay with the OrangePi but the interface lags and I have some mods I want to eventually do to my mill. I have the newest official RPi image running on a RPi 4b. I need to eventually marry this to an external motion board but I decided to start off with software stepping using a Pi hat, but I know that won't last long. Basically I'm done screwing around and want to setup a system that is capable and expandable EASILY.

I've been looking at the Mesa 7C81 but that is probably overkill for my purposes, but if it is truly as easy as it seems it may be my final choice. So first question is if setup of the 7C81 is as easy as it seems with the PNC config wizard?

Second question I have is whether I have missed another option that is less overkill.  Here is what I eventually "complete" my mill

• LinuxCNC running with touchscreen interface without lag or problems. Would eventually like on-screen keyboard with a wireless keyboard/mouse usable if needed.
• 4 closed loop steppers (XYZ and a rotary table)
• 7 home/limit switches (2 each on XYZ, 1 on rotary table)
• Spindle control (VFD)
• Spindle encoder for tapping.
• 3 encoder wheels (for using the machine as a pseudo manual machine)  
• Maybe a dozen or so switches/buttons for input to LinuxCNC
• Only need about 40 kHz stepping rate max.
  
  Should I just stop thinking about it and buy the 7C81 when it comes back into stock? Or is there an almost as easy solution that will fit the above needs.
  
  BTW, I am also planning to CNC my lathe and would want to duplicate the setup the mill has on the lathe so I don't have to relearn anything.
  
  Thanks in advance.

Hardware RPi 5 8gb
IMAGE rpi-5-debian-bookworm-6.12.11-arm64-ext4-2025-01-27-0140 (1).img.xz

On a fresh image install i get failure to start service in the boot.log below is from the journalctl

i formatted and tried again same problem any ideas?Feb 20 14:49:54 raspberrypi systemd[1]: Starting zramswap.service - Linux zramswap setup...
░░ Subject: A start job for unit zramswap.service has begun execution
░░ Defined-By: systemd
░░ Support: www.debian.org/support
░░
░░ A start job for unit zramswap.service has begun execution.
░░
░░ The job identifier is 119.
Feb 20 14:49:54 raspberrypi root[738]: Starting Zram
Feb 20 14:49:54 raspberrypi zramswap[738]: <13>Feb 20 14:49:54 root: Starting Zram
Feb 20 14:49:54 raspberrypi zramswap[734]: /usr/sbin/zramswap: line 53: echo: write error: Invalid argument
Feb 20 14:49:54 raspberrypi systemd[1]: zramswap.service: Main process exited, code=exited, status=1/FAILURE
░░ Subject: Unit process exited
░░ Defined-By: systemd
░░ Support: www.debian.org/support
░░
░░ An ExecStart= process belonging to unit zramswap.service has exited.
░░
░░ The process' exit code is 'exited' and its exit status is 1.
Feb 20 14:49:54 raspberrypi systemd[1]: zramswap.service: Failed with result 'exit-code'.
░░ Subject: Unit failed
░░ Defined-By: systemd
░░ Support: www.debian.org/support
░░
░░ The unit zramswap.service has entered the 'failed' state with result 'exit-code'.
Feb 20 14:49:54 raspberrypi systemd[1]: Failed to start zramswap.service - Linux zramswap setup.
░░ Subject: A start job for unit zramswap.service has failed
░░ Defined-By: systemd
░░ Support: www.debian.org/support
░░
░░ A start job for unit zramswap.service has finished with a failure.
░░
░░ The job identifier is 119 and the job result is failed.

tried this numerous times.
i get so far and then mouse won't work after a reboot. curser won't move and no light on bottom of mouse.
tried a powered usb hub.
any other suggestions?
hugh

You never specified the resolutions of your monitor nor your make\model of monitor so kind of hard to diagnose.

I think your best bet would be to google something along the lines of "RPi4B skewed login screen" if you get asked what operating system on any forums tell them Debian Bookworm with a kernel built from Raspberry Pi kernel sources. If you mention Linuxcnc their heads will explode and tell you to come back here. The thing is this is the first time I can think of this issue has come up on the forum, so not a lot of knowledge.
Whilst we can diagnose some issues others are out of out league, whilst we could offer suggestions we've searched for not having your particular monitor makes it a bit hit & miss.
The images we provide are just a Raspberry Pi kernel built for realtime plus some binaries need for the RPi, a minimal Debian Desktop install, ie no packages for editing images, playing music, chatting or office stuff, ie packages not essential to controlling a cnc machine. On top of that there is Linuxcnc installed which needs nothing special as it is a debian package, but updated from what you'd find in the Debian repos.
To be perfectly honest these current build method has only been in use since about late 2023. So far we haven't had any major bugs, and your issue seems particular to your site.
So far I've tested both the current Rpi4 & RPi5 images with a small HDMI touch monitor and a 4:3 17" monitor using a HDMI to DVI Monitor, none have shown this behavior.

haasme wrote:

Hi,
When I try to log in with rdp from windows 11, it accepts user and pass, but after the image displays something pixelated as if there were 100 miniature desktop . Has anyone else experienced this? (rpi 4 4gb ). Everything else works ok so far..
 

Hi haasme,

I have tried this dozen times or so, most of the times I had the results as yours. There were times when it worked, I don't know why. I have the desktop, and it responded quite well as well. BUT WHEN I ran glxgears, its own windows with the three gears were pixelated as well. I have since given up on this remote desktop connection. I plan to have another desk and another monitor Or perhaps a HDMI switcher (if there is such a thing.)

Best regards,

...behai.
 

It would be better to have some protection of course, the same as with a Raspberry. The pin header can be used via the driver made by Guglielmi:
forum.linuxcnc.org/18-computer/48079-can...cnc?start=200#273554

For Rockpro64 (rk3399?), I built an image before for a Orange Pi 4, but that didn't seem to work well, spikes to 130us, could work with Mesa though. You can try to build one via Armbian, from 6.12 and up you don't really need to patch it, just the right configuration. Then experiment to isolate cpu1 and move the rt tasks to that core as explained in the following post:
forum.linuxcnc.org/18-computer/48079-can...cnc?start=280#286432

You commits caused somewhat of an issue. Do you think I sat on my hands and did SFA ?

I don't care about your workflow, it's not my issue. My issue was ensuring the integrity of the images.
I don't care about you trying to setup a remote desktop, that was something you decided to do. That software was outside the scope of the software needed to run a cnc machine. I don't know why people ignore using ssh.

I just tested this at the beginning of rt_peripheral_init and it compiles and works on my RPi5 and RPi400 if you include the attached dtcboards.h:

int rt_peripheral_init(void)
{
    FILE *fp;
    int i, j;
    char buf[256];
    ssize_t buflen;
    char *cptr;
    const int DTC_MAX = 8;
    const char *dtcs[DTC_MAX + 1];
    
    // assume were only running on >RPi3
    
    if ((fp = fopen("/proc/device-tree/compatible" , "rb"))){

        // Read the 'compatible' string-list from the device-tree
        buflen = fread(buf, 1, sizeof(buf), fp);
        if(buflen < 0) {
            rtapi_print_msg(RTAPI_MSG_ERR,"Failed to read platform identity.\n");
            return -1;
        }

        // Decompose the device-tree buffer into a string-list with the pointers to
        // each string in dtcs. Don't go beyond the buffer's size.
        memset(dtcs, 0, sizeof(dtcs));
        for(i = 0, cptr = buf; i < DTC_MAX && cptr; i++) {
            dtcs = cptr;
            j = strlen(cptr);
            if((cptr - buf) + j + 1 < buflen)
                cptr += j + 1;
            else
                cptr = NULL;
        }

        for(i = 0; dtcs != NULL; i++) {
            if(        !strcmp(dtcs, DTC_RPI_MODEL_4B)
                ||    !strcmp(dtcs, DTC_RPI_MODEL_4CM)
                ||    !strcmp(dtcs, DTC_RPI_MODEL_400)
                ||    !strcmp(dtcs, DTC_RPI_MODEL_3BP)
                ||    !strcmp(dtcs, DTC_RPI_MODEL_3AP)
                ||    !strcmp(dtcs, DTC_RPI_MODEL_3B)) {
                rtapi_print_msg(RTAPI_MSG_ERR, "Raspberry Pi 3 or 4, using BCM2835 driver\n");
                bcm = true;
                break;    // Found our supported board
            }else if(!strcmp(dtcs, DTC_RPI_MODEL_5B) || !strcmp(dtcs, DTC_RPI_MODEL_5CM)) {
                rtapi_print_msg(RTAPI_MSG_ERR, "Raspberry Pi 5, using rp1 driver\n");
                rp1 = true;
                break;    // Found our supported board
            }else{
                rtapi_print_msg(RTAPI_MSG_ERR, "Error, RPi not detected\n");
                return -1;
            }
        }
        fclose(fp);
    }else{
        rtapi_print_msg(RTAPI_MSG_ERR,"Cannot open '/proc/device-tree/compatible' for read.\n");
    }    
    
    if (bcm == true){
...

I was after 12 hours of milling parts in the shop, and another 5 hours of trying to set up linuxcnc, so don't be too angry in your judgment.
I also solved the problem as follows:

sudo nano /etc/X11/etc/X11/xrdp/xorg.conf
search for OPTION "DRMDevice" line
and replace with
Option "DRMDevice" ""
save, reboot and all work fine after!

I don't know why you insisted on saying that it was so, when I clearly told you I created the images and did not have those software packages installed.


Sometimes I don't know why I even fucking bother.