Martin Cowen ⁽⁴⁵⁾

A common problem in embedded firmware development is having to develop routines which read-in a given signal. Usually you have a sample device available which can produce the required signal on demand, but it is not always quick and simple to get this signal when you need it, and to get an exactly repeatable version of it. For example, if it is a sensor signal, then the signal will vary according to the sensed parameter (temperature, humidity, light) and will vary just due to noise so that it is difficult to get exactly the same signal twice. Even if you have the sample device and it can be made to produce the signal, it can be bulky, heavy or power consuming and so difficult to have on your desk along with your prototype hardware. Therefore there is often a need…

When faced with the task of reading in an asynchronous bit stream (i.e. one without a separate clock pulse line), the best solution is to use an onchip UART peripheral. However, there are many cases where it isn't possible to use a UART, for example: The micro has no UARTS, or the ones it has are already used. The pin can't be assigned to UART receive function - simpler micros have fixed pin functions; even in more complex micros not all pins can be mapped to any function. The base clock doesn't allow for the right UART clock rate with any of the possible divider options. The bit stream doesn't correspond to UART format, for example - more than 9 data bits, Manchester encoding, non-standard number of start and stop bits. The bit stream has a wide variation in pulse…

My trusty NAD 502 CD Player, which I bought in 1996 from Richer Sounds, developed a fault a few months ago. The display went completely dark, so although it would play CDs perfectly, it was tricky to operate. Luckily it was not a failure of anything more complex than the backlight, which turns out to be a couple of wire-ended small capsule lamps. This CD player has a fantastic specification and had great reviews at the time, so I was not in a hurry to dump it for a newer model just for the sake of some tiny and cheap lamps in the display. This really is built-in obsolescence because any incandescent lamp will eventually burn out, and these are not even replaceable without soldering. I suppose it was a cheap option at the time, and maybe the design life…

As an embedded engineer, I need to be able to see signals on the board under test in a reliable and trustworthy way. It is important to see a few signals on the same display to be able to measure time differences between them, so a multi channel oscilloscope is essential. Whilst it sounds like it would be a good idea to see as many signals as possible at once, this is only possible on a logic analyser, which reduces the analogue nature of the signals to a digital one. Logic analysers are great for multiple signals, once you are sure that the digital waveforms have the right analogue characteristics - high level, low level, rise time, fall times, ringing, spikes, noise, gitches on the edges. The logic analyser will hide all that from you and always show perfectly squared…

This had broken due to the weight of the items in the drawers causing the brown plastic runners to break. It's not that easy to find replacement runners, and in any case, they are likely to break again if they are used with this much weight - the unit is clearly designed for clothes, not paper files. It was clear that I needed to find a metal runner that could fit in the same slots to replace the plastic runners. Luckily, the slots in the drawers are a standard width and length: 17mm width and 350mm length, so these metal runners fit. They need securely fixing into the chipboard side panels, but an ordinary wood screw is not going to be able to take the weight. The pressure on the bits of chipboard just under the screws would be too…