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| Howto: Designing POS equipment like a Pro |
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| cavac:
Over the last few years, i had to work with a lot of Point-of-Sales hardware, and here is what i learned from established, professional equipment manufacturers: * Make sure to re-use the power connector from the previous version, but change the voltages. * If you can't change the voltages, swap the pins around in your power connector without telling anyone. * Make sure you use the same type of connector for different, incompatible things and place them next to each other. Nothing is more "Pro" than having Ethernet, Serial and the 24V cash drawer connector all use RJ45, placed next to each other in a place where it's hard to read the labels. * Make sure to run as much of the components as possible right at the upper edge of their specs to provide the shortest service life possible. * As a bonus, make your power supply voltage drift up to very high levels when the device is not connected. That way you can kill more devices if the power supply is plugged into the wall before it is plugged into the device. * If forces to support PoE, roll your own version that is incompatible with any other PoE injector or switch and make sure it fries any equipment not manufactured by your company. * When designing a printer, be sure to use an optical end-of-paper sensor instead of a mechanical one. The mechanical sensors are way too compatible with different paper types and are way too reliable in dirty environments like kitchens and bars. * Always choose touch screens that are easy to break with long fingernails. As a bonus, choose a touch screen that requires very strong pressing in the first place, so users are more likely to use too much force. * For mobile devices: Always use the most common radio band to get the best chance of outside interference. If at all possible, make it very low range to force the customer to put up base stations every 2-3 meters. * Make sure the batteries of any mobile devices charge very slowly and make the battery connectors wear out quickly. Nothing pleasures the customer more that intermittend faults. * Be sure that your cash register always messes up it's database if there is an unexpected power outage. * Your cash register should only work with printers that have a very specific, very outdated firmware version. * If you are forced to support external screens, always choose VGA and never support anything else than a 4:3 resolution. * Use the 20 digit serial number of the device as the default password and put it in a place where it's impossible to read and input at the same time. As a bonus, include lowercase 'l' and uppercase 'I' in the serialnumber. |
| daqq:
Not limited to PoS stuff: When in doubt, use a proprietary, ideally fully custom connector. |
| Sal Ammoniac:
Damn, I'm disappointed! I thought I was going to get a lesson in how to design piece of shit equipment like a pro. |
| cavac:
--- Quote from: daqq on December 10, 2021, 07:39:11 pm ---Not limited to PoS stuff: When in doubt, use a proprietary, ideally fully custom connector. --- End quote --- For added fun, use a parts number that matches a very common electronics part or spec. Let the user have fun googling the "555 connector" or the "RS485 video cable". |
| SeanB:
You forgot that your install media is use once only, and that to reinstall you need to order a new set of media from the supplier, who will send you a nice new to you set of 3.5in diskettes, provided you send in your old media first. They also will take 3 weeks to process the return, before sending you the wrong set of diskettes, or where disk 17 of 33 is faulty, and will not read properly. Also be sure to include a hardware dongle, which absolutely has to be connected to a proper Centronics standard parallel port, which has to be the type with open collector outputs, and with a 5V termination supply, and has to be LPT1 as well, at the standard XT base address. The dongle will not work reliably with any sort of multi IO parallel port, and definitely not with any EPP port, but strangely enough will work at least the first time you use it, but will randomly fail afterwards, and brick the dongle. Otherwise use a serial port, but have an external serial to RS485 converter box, powered by a cable led out through a hole in the PC case, and with thin wire connected to a socket, attached to the 12V power supply rail. As a bonus the software will only work with a genuine 16450 UART chip, as it uses features not actually used on the original PC, and thus not implemented on the later ASIC versions, and definitely will not work with the 16550 or any on chipset emulations. |
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