Modern microelectronics assembly requires clockmaker or robotic precission; sub-millimeter discrete components or pinout of integrated-circuits is nothing unusual. Building such highly integration devices from scratch at home is a virtually impossible, sometimes though fixing them with entry-level tools is still feasible. Continue reading
Measuring water level is fundamental goal of WLS experiment, hence its code-name (Water Level Station). Early summer 2014 hardware and software system had enough base services to make addition of entry-level pluviometer easy. Prior to PCB redesing for chinese factory I blueprinted and bread-boarded extra input circuitry in couple hours. Software part took me couple more days and my balcony-mounted station started measuring precipitation mid summer season. Continue reading
Visiting Jordan three years ago I was thrilled by the outstanding Dead Sea. Choosing seaside I had no time for Petra. Once I was requested to get there again I instantly knew where to go this time. Attracted by ancient city with thousands of carvings in rock with the iconic Treasure temple, place of Indiana Jones shootings, I decided to make a run through the rose red desert place. Continue reading
With the advent of 2nd revision of WLS experimental hardware I got nasty system freezes on ported firmware. As they happened always close to power cycling of probe section I suspected new ADC chip using I2C bus. Past experience with I2C drivers freezing system led to tests revealing bus corruption caused by non-deterministic behavior of slave during transient power rail states not isolated on time by the TXS0102 voltage shifter. Continue reading
So you got SIM900A, cheaper version of SIM900 with the same pinout/functions and 2-band instead of 4-band GSM radio, just to stumble on logging to network. While its great for Asian GSM infrastructure in different places in the world you will just get “PH-NET PIN” response meaning its locked for current network. I found that flashing SIM900A with firmware for SIM900 opens it up again to work exactly as SIM900, with slightly worse signal quality due to physical radio differences. Continue reading
These days turning imagination into reality at home is more real than ever. RepRap movement made fused deposition modeling technology affordable. Turning a figurine or mathematical object into physical object is exciting and funny and using 3D printer to fabricate mechanical constructions or replacement parts makes it another tool on a workbench. Yet 3D printing is far away from “Ctrl+P… ready” approach. Continue reading
Working prototype device made of modular PCBs let me go for the next step. Learning the process of professional PCB production in factory and making short series to scale out number of devices in the field. I had to get good grasp of CAM processing, gerber files review etc. but what bothered me more was the price. With the advent of internet services for prototyping it become easier and as always Chinese had beaten the others.
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For prototype I estimated that 128kB or flash would suffice and I was right; firmware took 75kB even though fatten up by embedded strings used across the code for tracing. On the other hand 4kB RAM of Atmega128 turned to be almost insufficient: I had to tune stack sizes of tasks with ten-bytes precision. Tests were running for weaks without problem, yet extra function added in chain of calls could potentially corrupt memory. I had to make more room to avoid hard to debug problems before field deployment. Continue reading
When I found inner part of liner torn in many places it was time to look for new skates. Powerslide Metropolis 2011 was good pair of boots already proven in urban stroll in dozen places on four continents. Getting new liners was virtually impossible so I decided to get new boots and sell out old pair for parts. Two days later I got 2013 model at home. And I could keep silent with replacement if not a little disappointment. Continue reading
Digital subsystems with different supply voltages have to align their logical states if they want to talk to each other. It can be done with variety of discreet components as well as dedicated integrated circuits. It is simple task these days with google. Things get trickier if one side needs to be powered off, to save energy for a start. Testing each case scenario with breadboards gives early warnings if something is wrong. I was just too brave skipping this scenario. Hit back by nasty problem I had to develop new skill: patching hardware. Literally. Continue reading
