22 March 2022

Again problems with LiquidCrystal_I2C Arduino library

I am having issues again with third party Arduino code that uses the LiquidCrystal_I2C library. The code was written in 2015-2017 and since then the said library has been hijacked, abandoned and is not backward compatible. In other words: it doesn't work. But I mostly do not like the "hijack and abandon" part.

The second part of the problem is using a mjkdz I2C adapter that reacts on address 0x20 but has a different wiring to the display, let alone the IC part number scratched off. This adapter needs a flexible library that allows remapping the PCF8574x outputs, which is not the case for most common LiquidCrystal_I2C. Or custom code and direct I2C drive. No thanks.

Conclusions of few hours spent debugging this stuff are:

  • throw away mjkdz modules so I don't fall again in the same mistake few months from now;
  • use LiquidCrystal_PCF8574 to avoid ambiguities and LiquidCrystal_I2C hijacked libraries: they are 95% compatible (just chance the instantiation and call to begin method)

05 March 2022

February 2022 news

I haven't been inactive in February 2022, I've just not updated the blog.

I have been playing extensively [time permitting] with WE 439A/6167 dekatrons, trying to get them spin reliably, which I haven't succeeded yet. In return I found out that they did contain a bit of radioactive material which is not indicated on the box nor on the glass. I am still unsure which isotope they used, since it is still pretty active after 72 years.

After receiving a small batch of IV-22 VFD displays from Ukraine and planning a clock, today I re-checked the Bad IV-27M bought in 2016 and, with the correct datasheet, I found the filament on pins 4+5 and it does light up properly. Hooray! By the way, the filament runs at 3V 160mA and segments light up with 12V.