Hey folks 👋 , anyone here know if the HATs for Raspberry Pi 2/3/4 work with Zero too? And is it only one HAT that you can have? I do not mind getting an RPi 4. Basically I want to have a fun project setting up 3 4G LTE modules with an RPi and do automatic failover or retries when there are network issues. I know this is not really needed since manually switching networks is fine for me, but never say no to a toy project.

All 40 pin models have the exact same pinout, just as all 26 pin models have the exact same pinout. So a hat that works on RPi 4 should work on the Zero since they both have a 40 pin connector.

Thanks @helpful-gigabyte-47939, makes sense. HATs I am looking at are 40 pin. So should be OK. But after seeing prices of USB LTE dongles I feel RPi 4 with multiple dongles is much better way to go.

@wide-carpet-65149 make sure to have an externally powered USB hub if using USB dongles, otherwise connection will be weak Better option: buy 4G CPE and do the switching in raspberry pi either using different IP ranges or using VLANs (if supported by the NIC)

@wide-twilight-82330 thanks, I am not aware of the power draw of the dongles. Externally powered USB hub is a good solution in that case. Will have to check forums. Also, stacking HATs is not possible from what I read in official docs. My initial thought was to actually load-balance multiple 4G LTE routers with Ethernet, but then that is just too much equipment.

@wide-carpet-65149 more equipment and cost aside, that set up is likely to give superior coverage / speed because you can add stuff like external antennas to each CPE.

@wide-twilight-82330 yep that is the main benefit. I am waiting for the rainy season to hit here (few weeks) and see how things go. I might really need to setup a CPE based if things are bad. But it is a not cheap experiment then. And my priority will be to first get the power backup. The telecom towers here all have power backup thankfully.

There are actually multi-sim routers available in China/Taiwan (mostly directly via ODMs), but getting them in India can be a challenge. Sadly, no OEM sells it in India.