New weather station build

 Oh no! The large 40x4 LCD I have is too big for the enclosure I have, and want to use. The next size up enclosure with transparent front is twice the size, so whilst would fit the LCD there would be much wasted space and it wouldn't look right. So I can use a 20x4 LCD that will fit, but only half the display of the big one. I'll use the 20x4 for now and then change to the 40x4 if I find a suitable enclosure. I like the full transparent front and opaque back and sides. Fully transparent and it would look like a glass lasagne dish and I can't see the innards with an opaque front. Having the transparent front is great for looking at the condition of the boards inside and spot any water ingress, or trapped moisture, or anything that shouldn't be in there.

 

I have stripped down the air temperature and wind direction/speed boards. I think I am going to have to do a lot of work with the wind direction indicator LEDs as they are common'd in 3x 10 and 1x 6, which isn't going to work with the MAX7219 ICs, so I suspect a lot of chopping tracks and wiring will be needed on that. It does look like 7 segment LEDs should be much easier. I just need to test some code that apparently makes the MAX7219 work with a common anode. I have ordered 10x MAX7219 ICs so I can have a play about when I receive them. 

 

 

It would be rude not to.... 

 

Progress!!! 

 

MAX7219 LED controller (for common-cathhode LEDs) running common-anode 7 segment displays. The brightness isn't quite what I could like, but it should be fine. I may be able to tweak it a little, but the MAX7219 wasn't really designed for running common-anode, so if not, I can't complain.

 

Now to make up a little daughter board with the MAX7219 and try it out for fitment/space etc. If all is good, then I'll make some more and get teh display boards retrofitted with the new controllers. This IC will daisy chain too, but I might have to get a little clever with the code as this is just addressing the SPI bus directly. It's not using any specific library. Should be doable though, and maybe with some more clever programming I might be able to daisy chain the wind direction indicator onto that. That would be ideal, and then use an ESP32 to run the displays and all of the individual LEDS. Of course, since I am only using 5 of 8 digits, I may be able to use the spare digits for the individual LEDs. Which ever way it works out, I'm super pleased I managed to get the original 7 segment LEDs working. 

More progress! 

Yes! They can be daisy chained! Each display has to be selected using the chip select pin so a small for loop will cycle through each display, select it and write the numbers to it. That is really good news as it means I will use less MCUs for the display. It may even be possible to get everything running on one ESP32. I'm using an ESP8266 right now just for testing.

What you can see in the video (but too fast to see with the human eye) is the right display is selected and written to, then the left display is selected and written to, and then it loops around. The numbers are just random numbers. Each one generated for each display, each cycle.