I am working on a senior design project. I have connected the BQ26500 as shown in the data sheet with a 10kohm pull-up resistor on the HDQ line. I am using an ATmega 48PA microcontroller to read battery capacity. I am also using USART as described in TI's HDQ Comms pdf with the exception of TX pin connected straight to the HDQ line.
When the microcontroller transmits via USART, it is able to pull the HDQ line low(~0V). The BQ26500 responds but is only able to pull the HDQ line down to approx. VCC-0.3V instead of 0.3V.
I have tried connecting the TXpin to a MOSFET as in the HDQ comms pdf but had worse results(i.e. no pulldown by the BQ26500). As well as, disconnecting the RXpin and disabling the microcontroller's internal pull-up resistors.
Wondering if anyone has any ideas on how to fix this problem and more importantly why it is happening?
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