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Showing posts from October, 2017

CTC / Mightyboard serial Wifi conversion fail

This is just a quick post while I'm working on something bigger. I've tried to get a NodeMCU module to interface to the serial port on my CTC Dual/Bizer printer, which uses a Rev G(?) Mightboard motherboard. Unfortunately, the main serial port is not exposed, just UART1. The easiest way I've found to get to the TX/RX lines was to piggyback on the resistors just before the ATMega8U chip: The 8U is used as a serial to USB converter. 5V and ground can be picked up from the exposed UART header, pictured bottom middle: I tried to use the ESP3D firmware but it only works with boards that support G-Code, not X3G. So I abandoned the project due to lack of time. The pictures above are from a few weeks ago but just yesterday I managed to put a hole in my 8U chip, no idea how that happened: So now I was forced to use my makeshift serial connection. I tried both possible solutions: https://github.com/beckdac/ESP8266-transparent-bridge https://github.com/jee

Voyager Golden Record images - processing considerations

As you may have seen in my previous post, decoding the images on the "Golden Record" is not very difficult. The problems arise in timing and amplitude issues. I've talked about timing in my previous post: there "sample rate" varies throughout the record (slowly increasing speed) and it also "flutters" throughout a frame. The amplitude issues are caused by feeding digital signal into an unconditioned/untuned analog system (probably a recording needle). Let's analyze the circle image: I will use the [vertical] scanline represented by the red dot as illustration for how a uniform background (constant color) should look. The blue trace is the actual waveform. My red line underlines the non-linearity of the recording. The yellow line signifies my expected value. So we have an inverse exponential gain that needs to be applied with respect to time, as well as a linear gain. The could be mixed into a single formula. For reference, the

Decoding Voyager Golden Record images - in Java

My inspiration started when I first saw the associated video for this article:  https://boingboing.net/2017/09/05/how-to-decode-the-images-on-th.html Without studying much further, I decided to download the sound files and try my hand at decoding the images - more as a programming exercise. I haven't studied the original article too much as I didn't want any spoilers. After struggling a bit with the data, I found that the article could not help anyway with the problems I was having. So there's the "cheater" disclaimer. Watch the end of this post for updates. Data preparation Load the sound file into Audacity, perform a normalization (Effect -> Normalize) to 0dB. Then click the black triangle above the track name and do "Split Stereo to Mono". Select one channel (entire width), File -> Export Selected Audio. I used WAV 16-bit PCM as I couldn't get MP3 to work properly in Java. That's how the waveform should look. Get famili

Zoom 9002 hardcore repair - basket case

Many years ago (circa 2004) I bought a used Zoom 9002. This worked fine for a while until the output became weaker and weaker. At some point it stopped amplifying completely. I looked online, there was at least one blog post mentioning that some electrolytic caps and the ICL7660 need to be replaced. I did that, nothing improved. I think the display also started failing. "Smart" as I was at the time, I decided that perhaps the board needed some reflowing, so I stuck it in an oven for a few minutes. Packed it good. Fast forward 10 years later: Initial condition This was literally a "basket case" - all the parts were in a basket, with no ideea what goes where.