Straight after releasing v3.0, I knew there was room for some improvement. Not that v3.0 was bad. Yet there where some things that needed to be addressed…
UCB C “bug” 🐞
Yeah I know, I was complaining about the USB-C from the Raspberry Pi wasn’t fully compatible. The more advanced power adapters weren’t working on the Raspberry Pi, and neither on my P1 ethernet reader. I was fine with that, knowing nobody would use an powerful and expensive power supply to power it (in case of older meters). And the “simple” cheap USB-C adapters where all working fine. So why bother?
Well it kept bugging me (literally). So I read some documents about the standards and soon found that the easiest solution was to place two resistors of 5.1k, one to each cc pin and to ground.
Power converter 5v > 3v3 🔋
Since the beginning I was using the LM1117 3.3v LDO (low drop out) regulators. Why? I knew they where good! They’re also quite beefy, as well as price, as capability. They can handle up to 1 amp and cost me about a euro a piece. Sure I could find them cheaper on AliExpress, yet some components I want to choose for better quality and came from Farnell. I know, most would say that they’re all the same. A voice in my head told me to go for that.
Yet why go for 1 amp versions, if you only need 250mA max? (that’s what the P1 port from DSMR 5.x can provide). So I found these smaller and cheaper ones. The ME6211C33M5G-N. The are rated for 200mA normal use and 600mA max. These should do perfectly. Also they’re small, it has the same package as the inverter I use: SOT-23-5.
The result: v3.1
Well, it is exact the same as v3.0. The only difference is what’s between the pcb’s. Here you can see the regulator and inverter next to each other (LDO1 and U2):