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An [[electronic]] device or [[embedded system]] is said to be '''field-programmable''' or '''in-place programmable''' if its [[firmware]] (usually stored in [[non-volatile memory]]) can be modified "in the field," without disassembling the device or returning it to its manufacturer.
== Motivation ==
This is often an extremely desirable feature, as it can reduce the cost and turnaround time for replacement of [[computer bug|buggy]] or obsolete firmware. For example, [[as of 2007]], a [[digital camera]] vendor could distribute firmware supporting a new image format by instructing consumers to [[download]] a new firmware [[ROM image|image]] to the camera via a [[USB]] cable.
== History ==
When a device's firmware is stored in [[mask ROM]] or [[one-time programmable]] PROM, it cannot be modified without physically replacing the [[integrated circuit]], so such a device cannot be field-programmable in the modern sense. [[EPROM]]-based firmware can be erased and reprogrammed, but only after lengthy exposure to a high-intensity ultraviolet light source.
Thus, field-programmable devices were not practical until the invention of [[EEPROM]] and [[flash memory]] in the 1980s. Early EEPROMs could only be reprogrammed with expensive, dedicated [[programmer (hardware)|programmer hardware]], since they required high voltages (10-20 [[Volt|V]], compared to typical 3-5 V [[logic level]]s) and there was no standard programming [[protocol (computing)|protocol]]; as a result, field-programming was mostly performed by professional technicians and service engineers. However, as of the early 2000s, many devices were expressly designed to be field-programmed by ordinary consumers. Several developments have made this possible:
* Modern EEPROM and flash devices contain internal [[charge pump]]s which eliminate the need for high voltages.
* Most consumers have access to [[personal computer]]s, which can perform arbitrary programming protocols.
* Ubiquitous [[Internet]] [[Internet access|access]] provides a convenient means to rapidly distribute firmware images.
Standard protocols for programming non-volatile memory devices have emerged. For example, [[JTAG]] may be used to read and program the EEPROM and Flash chips in many [[consumer electronic]]s devices. Many such devices include JTAG [[header]]s internally for [[quality control|factory testing]], even though no external [[connector]] is exposed.
== Hobbyist opportunities ==
[[As of 2007]], many consumer electronic devices (including [[MP3 player]]s, [[broadband router]]s, [[cell phone]]s, and digital cameras) contain embedded systems based on [[general-purpose computer|general-purpose]] [[microprocessor]]s and [[microcontroller]]s. Most of these devices contain field-programmable components which can be located and accessed by knowledgeable [[hardware hacker]]s. Field-programming allows hobbyists to replace a device's firmware with new code that can modify or extend its capabilities.
Numerous online communities have sprung up around devices found to be particularly conducive to such modification. For example, the iPodLinux and OpenWRT projects have enabled users to run full-featured Linux distributions on their MP3 players and wireless routers, respectively.
While hobbyist field-programming is theoretically possible in practically any embedded system today, in practice efforts to modify consumer devices are often hampered by lack of [[documentation]] for the [[hardware]].
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