Raspberry Pi 4, which one to pick?

Hardware Questions and Recommendations
1

Hi. I hope it's my last topic. (well there's still access point left after this, but I am running out of budget)

I don't know which Raspberry Pi 4 version to pick.

There are no up-to-date benchmarks after all of the optimizations done in Linux kernel and raspberry pi OS. I mean, I will be running OpenWRT, but it should be similar results. And also the pricing. For the same price as the RP4 4GB I can get a package that consists of: RP4 2GB, power supply, case, HDMI cable 32gb sd card and ethernet patchcord. So which one to pick? 1GB isn't even available anymore and 8GB feels like an overkill.

Second question. Does RP4 support USB modems? I mean, not USB tethering. Straight USB modems. I have em7455 modem to be precise.

Last question. If this all works, can I just someday buy an access point (like for example xiaomi ax1800), plug it into raspberry pi ethernet and will it automatically work (or with switching few settings in the RP4 router) ?

2

There are a few things you might want to be aware of

Performance will be worse on OpenWrt without modifications as code (with a few exceptions) is compiled with -Os (simplified: prioritze binary size over performance). Unless you're really trying exceeding 1Gb memory usage using OpenWrt is hard as it targets "low-powered/end" embedded platforms in general. I would however advice you to get at least 4Gb unless you really know it's only going to be used for OpenWrt (it certainly wont hurt in the long run anyway). Not sure what you're going to use HDMI for, a TTL adapter will be much more usable and cheaper. You don't need a second ethernet jack? There's also no hardware crypto support which you might want...

USB modems are supported, you might need to do some tweaking on your own however. Keep in mind of limitations of USB on RPi SBCs, mainly potential bandwidth starvation (USB3 vs USB2 ports available etc).

As for the AP, it wont be any different compared to any other device

3

Yeah. At first for sure it will be only OpenWRT. But I can't say that it will stay for that always. I am fascinated by it being a good retro console especially given the Vulkan API. I also heard it's not a bad device as a tv box (not 4K though), pseudo NAS device and few other things. So sure, after it's done the work as a router I would use it for something else. I don't know if there will be any thing better than RP4, but something that eats less power would be nice, because if the RP5 arrives I would rather leave the RP4 as router and use RP5 for something unless RP5 comes with wi-fi 6 that can be turned to access point.

Well, at this moment for nothing, especially because I don't have any HDMI monitors. But you know, free stuff is free stuff. (well, not exactly free, but it's already a part of the RP4 package in the store)

Ok, I'll agree I'm dumb. How will TTL adapter be useful for a router or for anything?

As far as I'm concerned then no. Because I get my internet from SIM card and I only have 1 PC that doesn't have a wi-fi card. I was planning to get Intel AX200, but I wanted to upgrade my network first and so it can wait. So the RP4 will have just two ports used: USB3.0 for modem and ethernet for PC. And if I get an access point in the future then RP4 ethernet will be used for it and devices will be connected to it. Or do I need second ethernet jack for it to work?

Sure, sounds useful. But also from what I've read just now it seems that it is most useful for OpenVPN users. I don't use any VPNs and I don't plan to since I don't want to pay for them and the free ones aren't exactly great. Or can it be used for anything other?

I think 2 USB 3.0 ports will be enough. I can always get an usb HUB if I need more. I'm more concerned about power delivery because my modem can eat up to 5W and USB3 delivers a little less. But even my tests with USB 2.0 so far work and the results are better than my mi-fi router so I don't think I will have many problems.

That's a music to my ears. At least 1 device that I can get without worrying if it will work with my network.

4

You will probably want a powered hub to run a USB modem. The RPi itself uses a few watts, it's unlikely to reliably supply 5W additional to your modem.

5

TTL in this case refers to a serial connection (terminal), basically a way to see what's going on without hooking up a monitor. https://elinux.org/RPi_Serial_Connection
If you want something cheap an reliable go for CP2104 based ones such as (and so on):
https://www.diymore.cc/products/usb-2-0-to-ttl-uart-6pin-module-serial-converter-cp2104-stc-prgmr-replace-cp2102-with-5pin-dupont-cable
https://www.aliexpress.com/item/33052028317.html
https://www.makerfabs.com/cp2104-usb-to-serial-converter.html

One ethernet port will be enough, however LTE modems can be power hungry and there are numerous reports of USB(-C) @ ~5V powering SBCs (various) being a bad idea as voltage drops can easily occur leading to instability and other fun issues. Adding a powered USB-hub will mitigate the issue however be aware of backfeeding ones which might be a project itself finding a decent one also adding to the overall cost. There are other boards that support 9V or higher input to mitigate the issue however they might not still deliver more than 500mA over USB (depends on design).

As for crypto it's/can be used for various tasks, Samba (SMB), checksumming (files etc), VPNs and so on. If you have enough processing power you might get away with it anyway (without noticing) however that also means that there's less processing power left for other tasks.

7

I was considering that, but there aren't many greatly priced so it would need to wait. Also it would be good to find power supply that can both power the Raspberry Pi and usb HUB but that's a challenge.

So, can't I access the RP4 router through ethernet port or connecting through wi-fi? I mean in normal devices you just use the IP address of the router and voila. It doesn't work like that here? Or do I need TTL adapter for some advanced settings?

I'll read more on that.

Well, I think I'll pass with that. I don't think there are better priced SBCs that will also retain their value after a while and RP can always be used for something else than a router.

8

as long as everythign is working right. If for some reason you can't connect, like you borked your settings, it can be useful to have a serial port. But with the Pi you have the possibility of a monitor and keyboard as well. You don't have that in most routers. I consider this an advantage.

I doubt it can wait. The Pi4 is already straining its power supply a bit. It needs a 5V 3A power supply, adding an additional amp of current draw is likely to be very flaky. I mean, you can try it, but plenty of people report frying SD cards when power supplies fail to provide required power, so it's not risk-free.

https://www.amazon.com/Sabrent-Individual-Switches-Included-HB-UMP3/dp/B00TPMEOYM/

doesn't seem like it would break the bank.

9

To clarify, the RPi can work off a USB modem, but you need to get a supported one (i.e. one that has drivers in/for Linux).

In my opinion, the 4GB is reasonably price particularly if you are in the UK (you can get it off ebay for only few pounds more than the 2GB).

The specs should be fine for 4K decoding. The CPU is capable, and you have ample memory. My RPi3 plays FHD movies comfortably.

If Kodi is your cup of tea, OSMC is good OS; it's lightweight with Kodi built-in already (actually it boots and goes straight to kodi, but you could install packages and access it via SSH). So you could even make a RAID of two USB 3 disks and mount that on Kodi.

I think unless the RPi is very overloaded, 3A power adapter should suffice; it's presumably designed to provide enough power to Hats and/or some USB devices, so the 5W modem can substitute that. But I don't own the device anyway.

10

Have a look at my RPi4 powered LTE modem build using a EM7564 here: https://ltehacks.com/viewtopic.php?f=37&t=1591

For power, you'll definitely want the USB3 M.2 enclosure that ltefix.com sells. It has TWO usb3 connectors - one for power and data, the other just for extra power. An LTE modem can draw more power than a single USB3 can supply.

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11

Regarding power consumption, I have an Orange Pi PC2 (Allwinner H5) along with a Huawei E3327(s) dongle that runs stable using a 9W 5.2V PSU 1.8A at stock speed (whatever u-boot sets, I think it's around 670Mhz) however cold boots can fail sometimes. I haven't looked at it more if it's a PSU issue or u-boot (memory timing related) but it's running a fairly old version of u-boot :wink:

12

I imagine that's for the maximum load. I am only going to be running OpenWRT though so I think it should survive. Its not like it requires more processing than gaming, right?

Yeah, I think I'll try it. I mean, I did some tests of my current mi-fi router and my newest modem.

  1. Mi-Fi was connected using micro-usb 2.0 cable and it got 20Mb/s download 0.3Mb upload.
  2. Modem was connected through usb 3.0 hub (passive, I don't have power connector for it - 3.5 mm diameter, 2mm deep), then usb 2.0 hub and the usb 2.0 micro usb cable. And it got 28Mb/s download and 2.3 Mb/s upload.

Yeah, it's not the best it can be, but so far I'm satisfied and happy that it doesn't just randomly turn itself off because battery is dying (looking at you, mi-fi routers). The point is. If it could survive connected through usb2.0 then I don't see why it wouldn't work through usb 3.0. Not talking about max 300Mb/s download because let's be real I will never see that kind of speed on it.

Yeah, I think em7455 has the needed drivers for Linux. I tested it on newest Ubuntu Live and it did work without installing anything. Well I did install modem-manager GUI, but only to conveniently see some things.

Yeah, would be great. But unfortunately here the difference is nearly 50% more. And I bought the modem for less than this. It all really is a matter of pricing, because sure I can pay more for more RAM, but is it worth 50% increase in price? Like I wrote earlier I can get a whole bundle for 2Gb version and be done with ordering stuff. Also, would be good to pay visibly less for the whole project than consumer products. I mean the cheapest cat6 router that I can buy right now and is already assembled and with 2 year warranty is ~$130. So far the modem and the micro usb adapter enclosure with 2 mini antennas cost me $36 dollars which I am honestly amazed that you can get it for that cheap. That leaves us with $100 if we want to match the price, but where are bragging points in that? The bare RP4 4GB costs $76 right now. 2GB version costs $51. So yeah, I could get 4GB, but it all comes to how much better performance I can get

Yeah I've seen somewhere that playing local files should be fine, but streaming from Netflix has some issues and tearing. I don't remember how much RAM it had, but I assume 4GB since it seems like the most popular version.

Officially RP4 can deliver 1.2A to all USB devices combined. So my backup plan to use USB-Y cable is considered questionable. Fortunately it seems that the recommended supply is already considered to have reserves for usb ports (https://www.raspberrypi.org/forums/viewtopic.php?p=1507398&sid=66a0757d6ee0b8de8055d824b94de239#p1507398)

Oh, hi. I've read your topic. Good job. I definitely agree that this topic is a rabbit hole that I wasn't exactly ready to jump into. However I don't think I need something so complex. I mainly just want something similar to what is visible at the end of this page: https://github.com/danielewood/sierra-wireless-modems.
He's a wizard when it comes to the sierra modems. It would take much longer if not his scripts.

I think it's already too late for that. And I don't think if I can even have it delivered to Europe. So yeah I think I'll need to look for USB-Y cables.

13

That's a bit too much. I don't know where do you live, but that offecial price for USA and Europe are much less. It should be around 55 for the 4GB and 45 for the 2GB.

But if the numbers are as you say, then I would get the 2GB. It should be more than what you need for the router, should do OK for a media server, and by the time you decide it's not enough for you, there is RPi 5 in the market.

14

Yeah, I should probably include the fact that all the prices that I wrote include the tax. Which is over 20% in my place... and inflation also has a say in the price.

15

yeah, go for the 2GB version - it will fit your needs nicely.
Also don't consider the cat6 router as it would come with a lot of limitations like grayed out options and lack of support/firmware upgrade/security - you just can't compare it with Openwrt's flexibility/options

16

Just my 2 cents: take into consideration what range of WiFi you need. As a WiFi client, the RasPi 4 is fine, however as a WiFi router, given that the RasPi family uses copper cavity based antennae, you may need to think placement and range.

Note: this applies to all variants of the RasPi 4 (like the 400 keyboard too)

17

Well, I already missed the delivery and it won't be until January that I can get it. They have 4GB at stock though, but I will wait and see. Who knows, maybe there will be some surprise release or sales.

I mean, I'd be surprised if it even works because I've read somewhere that there were some problems. I mainly don't use anything outside my room where the RP4 would be placed near window. I'm not counting 2 rooms that are on a different level (and yeah, this building is old so pretty massive walls and ceilings, however weirdly m7350 can give a pretty good signal even on the low range setting since I can even watch youtube there), but I can live without using the internet in them. I think it would be enough, the Pi is Wi-Fi 5 and I only have Wi-Fi 4 devices so I can always just pick up another access point and plug it into RP4 (and it shouldn't be ridiculously expensive). But thanks, that means I can stop worrying about my current Mi-Fi dying before I can get an access point for my future router.

18

I would recommend to use access points only. The RPi4 is probably ok for a couple devices in the same room, but it's a crappy access point compared to an EAP225 for $60, so it's all about your budget and tolerance for low grade wifi. If you get yourself a decent switch and wire things in, the wifi may be less important to you.

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19

Hi, I’m using a Raspberry Pi 4 with 4GB as my router, so far without any issues, except that I think you really need a monitor or console to set it up, at least with my setup the interface didn’t came up automatically so no ssh right after a fresh install.

I have a switch (tp link tl-sg105e), my pi connects to it, as well as my cable modem and my ap (tp link as well, ac-1350).

That switch allows basic vlan so I can have my isp network (cablemodem) and my local network (ap) separated into the same interface of the PI for routing.

I’m also using wireguard vpn to connect to my home network from outside (office/mobile) when needed.

So far I’m quite happy with it, also consider getting a case with fan for the pi if you plan to store it in a drawer like I do :rofl: