Add support for a voltage monitoring pin

[raenye]

Hi,

Would you consider adding software support (like JYEtech did for the DSO138mini) for monitoring voltage on PA7 via a 3:1 divider?
Naturally it makes most sense together with a Li-ion mod.

Merci,
R.

[mean00]

The problem is finding a free ADC able pin
PA7 is connected to TestSignal, awkward to use as a voltage input pin

[raenye]

Theoretically one can free DB0/DB1 from the LCD and use them instead; even better - perhaps multiplex LCD and voltage measurement pin? after all, it only makes sense to sample battery voltage every 5s or so.
One could use J2's connection to DB0/DB1 and modify the encoder's 3v3 pull-ups to a voltage divisor?
This even allows to measure two individual voltages (e.g. for a 7v4 2S battery setup¹)

Footnotes

1. I had this crazy idea of using one large and one small li-ion batteries in series, with the full 7v4 going to the analog board, and the 3v7 from the large one used to power the LCD and the MCU. Together with a B0505S and two TP4056s, this allows charging both cells via a single USB input. During battery operation the 2S setup allows for smaller switching noise (just from the ICL7660). ↩

[mean00]

I dont know if that would work
DB0/1 are used as digital in/out, not sure it is a good idea to connect an analog signal (the battery voltage) there.

The other option is to use the 2nd I2C interface to connect an external ADC

(I looked at that in the past as i have li-ion battery mods in my 2 DSO)

[raenye]

Can't it be hidden behind a diode (and another digital pin that serves as 3v3 pullup)?
That is, battery -- large forward voltage diode -- DB0 -- digital pin (resistors omitted)
when digital pin is 3v3, the battery is effectively disconnected, and the normal LCD communication can be active;
when you want to measure vbatt, switch DB0 to analog, lower digital pin, measure, restore digital pinm restore DB0.

[mean00]

you dont really know how the LCD side behaves
Using a small mux is an option also, but it requires non trivial change

[FiusRa]

Hello. Haven't been here in a while. With past experiments, I burned a few stones and abandoned the dso. Let me remind you that I have a fake fee. one of the first. without stabilizers 7905 and 7805. at the moment I have finalized the entire analog part according to your posts. with the replacement of 084 and 082 with 074 and 072. the signal has become better. now firmware 064a/ for fake. I read here that with the installation of ad8066 in dso 138, the device began to see up to 1mgz. perhaps a remake is also suitable for 150. the question is how to spill the firmware on a fake with a stm stone. filled with the help of STMicroelectronics flash loade with a cp341 progromator. White screen. last time with dino firmware, Dso150STM32F103_vanilla came up to me. I want to try a new one. can you help me get started?
https://drive.google.com/file/d/1lzQlFXOq2Z_5uclFOH2eR5vWNjiQjaSW/view?usp=sharing
https://drive.google.com/file/d/13z6JRWlvq_LokcrmemqqMT7vMMrT6OBl/view?usp=sharing

[mean00]

I'm splitting your post into #6 for clarity