RaspPi4 and USB Boot

I successfully got RACHEL to boot on the Pi4 with an external 500GB SSD running USB3! Has anyone else done any testing on the pi4 and USB boot to test reliability and speed differences? I want to compare notes.

Hi @brandonks

Are you using the latest image that I made? I know @SHOMI and @giakonda are testing it right now to see how many devices can connect to the hotspot and they might be using an SSD.

Hey @jamesk I used your latest image but then I had to go through the sequence of updating the firmware on the rasp pi to allow USB boot and then replaced some of the bootloader files as well. We are also going to be doing some testing in the next few weeks. It would be great to look at how the extra ram on the pi and the load speeds of the SSD make an impact. My only thought is the wifi card on the pi4 might bottleneck the USB 3.0 speeds?

Also trying to get it to be an independent solar module… do you know anyone who has gotten that done successfully? I am thinking of a 12V panel with a DC/DC converter to 5V with a few 18650s under a BMS.

@brandonks - Ah okay. The latest image is being testing because there is a reported bug with the wifi firmware included with RaspiOS that limits the number of connected clients to as low as 7. Apparently it’s on the manufacturer’s end so they can’t modify it. I don’t have enough devices to test this. As far as I know the USB3.0 ports are on a dedicated PCIe bus now so that should help avoid previous bottlenecks, but the on board wifi could definitely still be a problem. Ultimately using a router with the Pi is going to give the best results.

My plan was to wait to hear back about the device limit and then make another image that is set up for Pi4 USB booting. I can make that for you if it would help in your testing to be able to reflash one.

I don’t have experience with solar but @SHOMI has tested with the smaller panels you’d buy on Amazon and @giakonda’s organization https://www.giakonda.org.uk/ work with larger panels. I have run RACHEL-Pi off of a portable battery for phone charging so you could get a panel that charges those and not have to make anything custom. ( To anyone who might be reading, don’t try that with a RACHEL-Plus ).


@jamesk Ahh I see, I think that I only have had a max of four clients so far. I can try to max out the devices connected on Thursday when we meet again. But definitely using a router would be better. If you would be able to make a new image set up for pi4 USB booting that would be fantastic, it would help to speed things along.

I did see that possibility with using a portable battery. My initial thoughts are those electronics are not built for that kind of simultaneous charge recharge which could limit long term reliability and quicker battery fatigue (especially in warmer climates), although less of a problem with li-ion. I was looking at a smaller charge controller and a connected 3s bms and that DC/DC converter. I’ll let you know our future testing/planning on that is as well. @giakonda 's organization looks fantastic. It’s a small world since I was in Southern Zambia the past two years and did some work with rural school solar design there.


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Hi @brandonks, If I can be of help please let me know. We did try running a pi3 as a workstation of an 80watt panel and a 120Ah deep cycle battery that worked quite well. I have run a Pi Zero off a 20Ah power bank. that lasted about 3 days before the powerbank needed recharging. One issue with the Pi Zero is it can only deliver 6 simuntaneous videos at a time, If you don’t have 6 devices then this is not an issue.
Kind Regards Howard

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Hi @giakonda
I am working to run a pi with a 25W solar with a 3s 18650 configuration. We did some energy metering and it seems that with RACHEL, the pi 4 draws a little over 1A with a fan and ssd with constant heat at 115 F. Should get that config together by Thursday for general testing
@jamesk I connected more than 7 devices to the Pi 4, I think 11? Not sure about where the top limitation right now is. If you do have an updated image I will gladly test it!


Hi @brandonks,

The new image with USB boot enabled will be uploaded later today. I’ll update you with a link when it’s there. Thanks for checking the limit that high. 11 sounds pretty promising! I was hearing as low as 5 from some sources so maybe they’ve found a fix :crossed_fingers:


@jamesk That sounds great with me! We will make sure to test the upper limits of our device with the on-board wireless and then I also want to make a test with it using an external wifi USB 3 plug in. I do have a question on modules as well. I know that we are essentially downloading a bunch of Khmer (Cambodian) educational videos that we are going to want to structure in a GUI similar to that of the Khan Academy Lite. Do you know of template modules and files that we could use and just modify?


@brandonks thanks again for testing. It really helps me having feedback on these images.

There is a module template with instructions on the github which is what you’d see on the RACHEL home page. It can be found at the link below with instructions

Once a link is clicked on that module in RACHEL, it should be set up to bring you to the main page for the module which is a normal html page. You may have to create that page from scratch but you can look at the ka-lite-ess rachel-index page and the index.html for inspiration. As far as I know ka-lite isn’t open source to modify directly or copy but I’m not sure.

I would start fresh and google open source website templates that have elements you’re interested in and put something together that suits your needs but is as simple as possible. w3schools is a great resource for info on individual things.

If you want help with a basic design please let me know and I can try to put something together for you when I’m finished going through my current tasks list. I’m very interested in your project as my girlfriend’s parents were Cambodian refugees. Will it be deploying in Cambodia?


Hey @jamesk thanks for the links and details for the index pages and whatnot. I went through the module-template before, but was hoping there was an easier way then making it from scratch. I don’t think that we have enough time to build one up before our pilot date. I’ll have some on on my team look at some open source templates in the meantime and see what we can adapt to our use.

I would love any help with a basic design if you have the time. We are trying to deploy them in the Ratanakiri Province, Cambodia. We have had some past projects there with STEM education and unexploded ordinances, but are trying to continue our partnership with a couple NGOs/stakeholders to take it to the next level of education outreach.


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Hi @brandonks,

You’re welcome and I’d be happy to try and help you reach that deadline. I do have some tasks I’m working on for other people but I can always find the time, especially when there is a deadline for a deployment. It sounds like a great project. When will it have to be ready for?

If you could provide me an example of what the content will be like, for example a video with some matching text, or maybe even a basic drawing or screenshot of what you’d like it to look like for each video I can put something together for you to get out in time.

This is a rebuild of the latest image that is set up with the latest USB boot loader.


I booted it on a Pi4 with a USB stick and it seemed to work. If the hotspot isn’t on by default please try “sudo rfkill unblock wifi”. Let me know how it goes and thanks again for trying it out.


Hi @brandonks I am very surprised that the current we just over an amp. I’ve always allowed for for at least 3 amps when using the Pi as a computer, rather than a server. The smallest panel we have used was 80W but that was running a Pi with a montior and LED lighting.
I don’t know what 3s 18650 means,sorry.
I have used a Pi Zero with 6 devices all running video from RACHEL-Pi (RPi) without any trouble.
I have used the Pi3 with 15 laptops at the same time, again to trouble. I would think you could get a Pi4 to cope with 30, but I’ve not tried that. We don’t use fans, in Zambia, where the ambiant temperature can go into the 40s.

@jamesk Thanks for getting the new image up! Let me talk to my team tomorrow to put together some kind of outline that we were thinking of for the module. How can I get that sent over to you? I’ll get the new USB image up on a stick tomorrow to test as well

@giakonda I know that there is a 3A max on the pi with a full load with peripherals which it sounds like you are doing with the screen. The 18650s are lithium ion batteries about double the size of a AA. 3s is putting them in series at around 11.1V. Regarding your overall project in Siavonga/Monze district in Zambia, I know a founder of Zayohub/ iSchools that works with educational content in Tonga. Have you heard of them? http://ischool.zm/#teacher-edition

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@brandonks you’re welcome! If you could message me a google drive link to a zip or something that would work well. I won’t need all of the content, just an example of what you’d like and I can set it up so that the rest is easy to input. If it works out, I can just add the rest for you then. Good luck testing :slight_smile:


@brandonks Yes, we don’t use them because they were very expensive and when testing the zedupad I found some issues.
We have been using the Raspberry Pi 4 as work stations with RACHEL Pi as the server and the Kolibri African Story Books, this latter module has more languages like Bembe and ChiTonga which we need.

@jamesk Sure thing, I will message you something later today or tomorrow. Quick question on memory for the pi4 that maybe @giakonda could also answer. Out of all the memory options 2,4, and 8gb, what would you recommend?

Hi @brandonks
I would go for the most you can afford.
The 8gig is really good and can replace most pc I see here. And of course the power consumption is terrific

I agree with @giakonda. The 8GB is more useful as a PC or other device as well. As a RACHEL-Pi server, the 2GB will work but is a bit low and won’t utilize the Pi4, the 4GB should be fine, and the 8GB is likely not going to get used before you run into other issues with the CPU or disk speed, but as a PC it will matter.

I should mention that to utilitize the 8GB of RAM you might need to use a 64bit RACHEL-Pi image when it’s up.