Raspberry Pi 400 for DCC

[Crosland]

Nice.

 

Flash drives vary a lot, with some being considerably slower than a USB3 SSDs This blog site is interesting  https://www.jeffgeerling.com/blog/2020/fastest-usb-storage-options-raspberry-pi

 

I generally turn the Pi WiFi into an access point for direct connection of WiThrottle/Engine driver devices. You can then ditch the wired Ethernet except when you really need to surf the 'net.

[KingEdwardII]

USB 3.0 Flash drive vs USB 3.0 SSD is not a straightforward choice and it took me quite a while to select the MyMemory flash drive that I eventually purchased. The SSDs are undoubtedly faster, but they are much bulkier and more expensive, also requiring an adapter cable of some kind. I have an SSD but I have now used this as a network storage device (NAS) attached to my main broadband router, which serves all the devices in my home for backup and for file sharing.

 

So I use the Flash drive on the Pi400 as a compromise between small size, cost and speed - way faster than the original SD card but slower and cheaper than an SSD would be. I selected the particular Flash drive based on it having relatively high speeds.

 

As for WiFi, I am still experimenting as to the best configuration. I could use the Pi400 as an access point as you suggest, but I'm starting by using the WiFi on my main router. The main router gives a very strong WiFi signal in the railway room and the handheld devices I'm using are multi-purpose and need good internet access as well as connectivity to the Pi400 for controlling trains. If I start to use dedicated handheld devices as throttles, I may change this setup. The DR5000 command station is also Ethernet connected to the main router - its WiFi has limitations on how it can be used and since the DR5000 is static, running an Ethernet cable to it is simple. 

 

One choice I have made is to use 5GHz WiFi - faster, and with much less interference than the 2.4GHz.

[Regularity]

On 10/11/2020 at 13:30, Crosland said:

You do, however, have to unplug the power supply from the Pi 400 and plug it back in to restart.

Is that not dealt with via the useful in-line switch you can buy?

 

[Regularity]

Thinking out loud, and given the small size of the wifi receiver for the mouse, why is it not possible to use the wifi capabilities of the Pi to connect directly to the locos (with or without the Sprog)?

 

I am thinking of something akin to the GTX-Connect and GTX-Control (and for larger scales) produced by Games on Track (I think their English language version has been translated via German and can be hard to follow) where the loco receiver takes power from a suitable battery unit of the rails, a wireless signal from the transmitter, and outputs the result to a DCC decoder, either mobile (loco) or stationary (accessory). I know that GTX is using the IM wave bands, but surely something similar to receive a DCC command over a 2.4GHz or 5Ghz wifi signal and to do any necessary processing to provide the control input into a simple H-bridge  (such as with a Maxim MAX14870 from Pololu ) should be possible?

 

 

(With acknowledgement to Martin Sant of Blueridge Engineering and Darrell Lamb of O Scale Dead Rail. The connections might seem odd, but this causes the amp to operate in “locked-antiphase" mode.)

 

I am thinking of something simple on the transceiver end, similar to the ProMini DCC transceiver, but maybe slightly less bulky, i.e. wifi dongle, signal conditioner (if required) and something to provide the necessary 3.3V [if necessary] and 5V regulated supplies, via the track or battery power, i.e. the TX box - if the MAX14870 could be added via some header pins, so a single board required just the 4 connections for power in and DCC out, so much the better.

 

[Crosland]

6 hours ago, Regularity said:

Is that not dealt with via the useful in-line switch you can buy?

 

LOL, what will they think of next?

 

I'd like to see them get USB-IF certification for that

 

4 hours ago, Regularity said:

Thinking out loud, and given the small size of the wifi receiver for the mouse, why is it not possible to use the wifi capabilities of the Pi to connect directly to the locos (with or without the Sprog)?

 

Nothing at all if you have suitable receiver modules.

 

BUT you need to have a very robust protocol to avoid interference. A lot of people have had issues using WiFi throttles at shows due to congestion on the airwaves.

[KingEdwardII]

On 12/01/2021 at 18:48, Crosland said:

I generally turn the Pi WiFi into an access point for direct connection of WiThrottle/Engine driver devices. You can then ditch the wired Ethernet except when you really need to surf the 'net.

That is definitely what I don't want to do. The reason is simply that the mobile devices I use are not dedicated to running only Engine Driver apps - so having internet access is important to them and so the house WiFi is the best connection for them. It is also necessary for the Pi 400 to have internet access for software installs & updates and it also needs access to the house LAN for file sharing, backups, etc. I could connect all the devices to the house 5GHz WiFi, but in practice, connecting the Pi 400 via Ethernet is straightforward and simple for me since the Pi 400 is static and there is an RJ45 wall port within a short distance. 

 

Mike.

[Regularity]

15 hours ago, Crosland said:

BUT you need to have a very robust protocol to avoid interference. A lot of people have had issues using WiFi throttles at shows due to congestion on the airwaves.

Ah. That's a good point.

What I don't understand is (well, there's quite a lot I don't understand, to be honest, but specifically...) I have been told by those more knowledgable than me in this area that the radio signal simply replaces the wires/rails for the command signal, so a simple Tx at each end (DCC output and DCC decoder) is all that is required, yet everything immediately gets into coding microprocessors/PICs/etc. Or the IM band boards, e.g. from Tam Valley DRS, are as big as - if not bigger than - the DCC decoder.

As an alternative to WiFi, could not something simple be done with DT type small TX modules?