HX711 - Power & Logic lines question

Hello,

I am using a 3.3 voltage chip to interface with the HX711 chip, but I power the HX711 chip with 5 volts. I have looked at the data lines coming out using a multimeter and it doesn't seem to go above 3.3 volts but it's hard to tell with a digital multimeter.

On the datasheet I see some 100 resistors on the data lines.

My question is do you guys think that this device is safe to communicate with a 3.3 volt system?

Here is the datasheet: http://www.dfrobot.com/image/data/SEN0160/hx711_english.pdf

Thanks for your help,

Cameron.

According to the datasheet, DVDD is to be connected to the same power supply as the MCU.

Thus, if you are applying 5V to the DVDD, but using it with a 3.3v MCU, you are using it in a manner contrary to the manufacturers specifications, and you probably shouldn't do that.

Under power supply options, it clearly states that AVDD, the analog supply voltage, can be higher than DVDD, and vise versa.

So... You should be able to use it, but you've got to have the 5v on AVDD and 3.3v from the MCU power supply on DVDD. Be sure you've you wired everything else right, of course - Do read the "Power Supply Options" section in the data sheet.

Your DOUT line from the HX711 to the MCU would assumedly be at 5V levels and more than likely in violation of the limits on whatever MCU you have it connected to. An AVR is VCC + 0.5V on any IO pin.

I don't see anywhere on the datasheet where resistors are on the data lines (DOUT, PD_SCK).

No the resistors are on the analog inputs, not the logic signals... For a chip like this the analog supply must be very clean, so derived from an linear regulator (which is why it has support circuitry for this). If the MCU is 3.3V just add another 3.3V regulator to generate AVdd as a clean supply (and able to supply enough power for the load-cell in question).