Contents • • • • • • • • • • • • [] Introduction Routers with a serial port AND working CFE (bootloader) can often be recovered with a serial adapter, using CFE low-level commands. Otherwise is required to debrick, if available, which can also replace a corrupted CFE. The last resort is to desolder the flash chip and use a programmer to flash CFE (if needed) and firmware. Serial ports are normally four or five pins on the router board. ![]() Iso image corrupted. I have a corrupted iso file which won't mount nor open via WinRAR. Recovery via WinRar only yields the message that the file header is damaged and that there is no recovery information. Any way I can save it? It's the image of an SACD, so even partially recovering the data inside the image (so that I get at least SOME, if not ALL songs) would be nice. Unless it has an OEM header, you have to either solder the wires to the pads, or remove solder from the holes to install an appropriate header. Some routers, and here is a link to some. [] Redhawk0 summary Serial cable can be either USB or DB9 connection type and be capable of voltage level shift to +3.3V, not just +5V. There are four connections required for Serial to function properly: Vcc (+3.3V), GND, Tx and Rx. Some boards are NOT marked with pin designation, so use a multimeter to determine power and ground to avoid shorting the serial cable TTL chip. The bootloader/linux bootup messages will only happen for a few seconds, and after that, the serial console will be silent - so even if you have the right pin you will not hear anything. Once you get the right pin, the Piezoelectric buzzer should make a screeching sound much like that of a 56kbps connection. Then you can guess at the Rx and Tx lines. Rx and Tx are labeled relative to the cable, so Rx line needs connected to the router's Tx, because the router labels are also relative to it, so Tx and Rx get crossed for proper connection. On routers with two Serial ports (Tx0/Tx1 and Rx0/Rx1), use the '0' ports for your connections (I've not seen a router yet that connects to the '1' side). Most people get along without a serial console for their device because they're able to flash a working firmware the first time - or are able to apply various recovery methods - and do all their communicating with the device over a network. However, some bootloaders don't have a “really failsafe” network re-flash feature, making a serial console one of the few ways to recover from a “bad flash” or an error in a user's own configuration. Most devices supported by OpenWrt have or can be modified to have a serial port. These serial ports typically provide a console to the bootloader and, when the firmware has booted, a console to the running system. A console to the running system will let you correct a misconfigured network, for example. Console access to the bootloader will often allow one to fetch and flash new firmware and may be the only way to do so on some routers if the firmware is not functional. Enabling a serial port, if there is not one already available on the case, typically involves opening the case and basic soldering skills. The cost of components is relatively low; a 10-euro/dollar project if one uses “eBay-grade” parts (which are likely sufficient). If one wishes a more permanent installation, mechanical skills in modifying the case may also be needed. About a Serial Port. ![]() Most routers come with an integrated into the and its pins are routed on the to allow debugging, firmware replacement or serial device connection (like modems). Typically, a router first starts its “permanent” which is responsible for the first steps of finding the OpenWrt firmware and starting OpenWrt running. During these early phases, the bootloader often gives information over the serial port and can respond to its own set of commands. These commands are not “OpenWrt” commands, but ones pre-programmed into the bootloader. Details on these commands can often be found on the device-specific pages on the OpenWrt wiki. Once OpenWrt starts running, it is generally possible to enter failsafe mode with a terminal program attached to the serial port. Either in failsafe mode, or with OpenWrt running in normal mode, it is generally possible to enter commands the same way one would if using ssh over a network.
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