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Author Archives: mojo

XMEGA USART unsets output direction on ports when disabling TX

02/02/2012 – 15:23

I noticed that if I set the TX pin of a port to output and then enable the USART it works. If I then disable the TXEN bit (necessary because with IR comms the TX line has to be held low during reception, otherwise the transceiver blinds itself) the TX port pin is reset to being an [...]

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Fix Windows 7 not booting due to missing AHCI drivers

29/01/2012 – 15:26

If you change mobo and chipset Windows might not boot due to loading the wrong AHCI drivers at boot time. To speed up booting it only loads the ones it thinks it needs, and once set is not designed to change. To enable them all again go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Msahci and change the Start key value to [...]

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Fix Firefox image decoding performance regression

27/01/2012 – 18:34

For some reason Mozilla changed Firefox to decode imagines only when they are visible, meaning that they now slowly appear as you scroll down a page instead of loading quickly in the background first. Seems like a misguided attempt to save some memory. The fix is to set image.mem.decodeondraw to false.

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Ebay location script fix

27/01/2012 – 18:32

Ebay broke it, I fixed it… Greasemonkey as usual. // ==UserScript== // @name Ebay-Location-Route // @namespace www.ebay.co.uk // @description Adds a link for the item location on google maps // @include http://*ebay.* // ==/UserScript== // Version 0.5 // author: knoe/MoJo //Configuration var home = “Nowhere”; //home var blank = false; //open [...]

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Gigabyte crapware

19/01/2012 – 14:12

Picked up a cheap ex-display Gigabyte mobo in mint condition. By all accounts it is a good board, but man do Gigabyte love “value added” crapware. Some examples: Auto Green – Sleep or power down your PC from a Bluetooth device. Since Bluetooth has a range of about 25mm it seems like it would be [...]

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The Novatech website is shit

19/01/2012 – 10:45

Just popped on to the Novatech site to check some prices and noticed how shit it is. For example, if you look at SSDs there is no capacity category, you can only filter by price range or manufacturer. That was crappy back in 1998, and 14 years later it is pretty much unforgivable. Novatech isn’t [...]

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RFM12B bit stream sync issue

22/12/2011 – 16:04

Been working with cheap RFM12B modules at work and discovered something interesting about them. A couple of things actually, the first of which is that the datasheet for the Si4420 IC it uses is much better. The main issue is that the serial data stream you get when receiving is not always aligned to the [...]

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Compile time asserts in C

21/12/2011 – 15:48

Assert is a useful function that checks a condition and outputs an error if it is not met at run time. Aside from generating some overhead in the code it is also pretty useless on microcontrollers because the messages go to STDERR and, well, there isn’t one. A much better solution is to do the [...]

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Scheduling uTorrent on Windows

03/12/2011 – 19:12

Sometimes I close uTorrent and forget to open it again before going to bed for overnight downloading. It cannot be scheduled via the Task Scheduler in Vista/Server 2008 and above because scheduled tasks can no longer display a GUI. This is a security feature designed to prevent shatter attacks which are a form of privilege [...]

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XMEGA TWI (I2C) bus pull-ups

24/11/2011 – 16:32

The XMEGA 128A1 and XPLAINED hardware guide both suggest that TWI should work with the internal port pull-up resistors. Those pull ups are 50K+ and don’t pull enough for most devices. In short external pull-ups, say 10K, are essential.