What Worked Easily
Any generic barcode reader seems to work OK, cash drawer and thermal printer worked fine (E-PoS was used in this case for the later 2 devices).
I pleasantly learnt that the bar-code reader works on any item code column even in reports thanks to customer’s insistence on using it to scan items. However in form tables like in Purchase Invoice it may not accurately find the actual code so I advised the users to just input last 4 digits of the bar-code for the quickest search/filter experience
Gotchas and Some Painful Experience
If using Wireless LAN do not use DHCP and also avoid default IP ranges like 192.168.0/1.* etc. Some other devices in the vicinity may be using these and would easily disrupt your client devices hence negatively affecting transaction posting or connectivity. Positioning of your wireless device is also critical to ensuring the signal is always available within your store. High-powered routers only cost a fraction more than the standard ones so that may preferred for better results.
Advice your customer to have power supply backup for the networking devices as well (in POS a bug that duplicates or triplicates the transactions seems to be occasioned by network latency issues due to power outage or fluctuations).
If using Offline POS ensure that Always remember history setting is applied in the browser to ensure your browser localStorage is not inadvertently cleared when browser sessions end or if already suffering from some connectivity issues as outlined above.
If customer requires a Fiscal Printer then advice them to consider an Electronic Signature Device (ESD) instead since the former requires integration (it only installs to COM port e.g. COM3 but is not visible under Printers & Devices) but the later is visible under Printers and Devices.
Adv: An ESD is also cost-effective since you just buy one and connect to it via the network (it forwards print jobs after signing them) hence you share it amongst the Till users who will have their own thermal printers.
Disadv: A FP device may be costly as you may need to buy one for each Till user if sharing one is not acceptable.
Business Things To Know
If you are quoting for ERPNext be aware of other things that may need to be done. Customer may be expecting that you have the Client PC’s OS + Anti-virus etc covered as well.
Some customers may ask for certificates of Installation/Completion etc
Lastly, these lessons are applicable for both on cloud and on premise setups
I just thought to share some of my experiences so let me know if you can relate or have other experiences we could learn from as well.