A discarded handheld computer from the 1990s has had its keyboard donated to a new Raspberry Pi-powered project after some careful reverse engineering
.Pseudonymous manufacturer “Sunshine701c” (hereinafter referred to as “Sunshine”) has designed a Teensy powered adapter that allows you to connect the keyboard of an old Hewlett-Packard 200LX handheld computer to a modern PC as a USB device – as part of an upgrade project of deceased examples.”I’m currently working on a project that basically plugs a Raspberry Pi into the case of an old [HP] 200LX handheld computer that’s broken,” Sunshine explains.
“This project started by modifying an old keyboard so that it could be used as a standard USB keyboard. I used an old Teensy 2.0 microcontroller and kbfirmware.com (very old I know) to [do] this, as well as a custom built-in Interposer PCB to accommodate the very weird pad spacing on the Teensy keyboard
connector.”Pseudonymous manufacturer “Sunshine701c” (hereinafter referred to as “Sunshine”) has designed a Teensy powered adapter that allows you to connect the keyboard of an old Hewlett-Packard 200LX handheld computer to a modern PC as a USB device – as part of an upgrade project of deceased examples.”I’m currently working on a project that basically plugs a Raspberry Pi into the case of an old [HP] 200LX handheld computer that’s broken,” Sunshine explains. “This project started by modifying an old keyboard so that it could be used as a standard USB keyboard. I used an old Teensy 2.0
microcontroller and kbfirmware.com (very old I know) to [do] this, as well as a custom built-in Interposer PCB to accommodate the very weird pad spacing on the Teensy keyboard connector.”Released in 1994, the HP 200LX was a handheld computer powered by an Intel 80186-compatible processor running at 7.91MHz and supporting up to 4MB of RAM, with storage expandability via a PCMCIA slot on the side of the device. Meanwhile, the current lowest -performance Raspberry Pi model is the original Raspberry Pi Zero, which has a 1GHz CPU and 512MB of RAM.Well, plugging a Raspberry Pi into an HP 200LX would be an upgrade – although Sunshine is a request. “I beg you,
please don’t tear apart a perfectly working 200LX for a project like this,” the manufacturer wrote “I took mine apart because the LCD and [motherboard] were both broken. Unless you’re in the same boat with both the keyboard and LCD broken, consider a different smaller keyboard, it might be easier to implement and use , I just use this to leverage old technology that would otherwise be abandoned.
“Pseudonymous manufacturer “Sunshine701c” (hereinafter referred to as “Sunshine”) has designed a Teensy powered adapter that allows you to connect the keyboard of an old Hewlett-Packard 200LX handheld computer to a modern PC as a USB device – as part of an upgrade project of deceased examples.”I’m currently working on a project that basically plugs a Raspberry Pi into the case of an old [HP] 200LX handheld computer that’s broken,” Sunshine explains.
“This project started by modifying an old keyboard so that it could be used as a standard USB keyboard. I used an old Teensy 2.0 microcontroller and kbfirmware.com (very old I know) to [do] this, as well as a custom built-in Interposer PCB to accommodate the very weird pad spacing on the Teensy keyboard connector.”Released in 1994, the HP 200LX was a handheld computer powered by an Intel 80186-compatible processor running at 7.91MHz and supporting up to 4MB of RAM, with storage expandability via a PCMCIA slot on the side of the device. Meanwhile, the current lowest -performance Raspberry Pi model is the original Raspberry Pi Zero, which has a 1GHz CPU and 512MB of RAM.Well,
plugging a Raspberry Pi into an HP 200LX would be an upgrade – although Sunshine is a request. “I beg you, please don’t tear apart a perfectly working 200LX for a project like this,” the manufacturer wrote “I took mine apart because the LCD and [motherboard] were both broken. Unless you’re in the same boat with both the keyboard and LCD broken, consider a different smaller keyboard, it might be easier to implement and use , I just use this to leverage old technology that would otherwise be abandoned.”In order for the keyboard to talk to the current system, Sunshine had to probe every trace on the flex circuit to figure out which key corresponded to which pin on the unusual connector.
With this diagram in mind, the manufacturer built an interposer board that sits between the keyboard connector and the Teensy 2.0 microcontroller board – which in turn listens for keypresses and sends them to a modern host via USB.
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