Hi. I'd appreciate any help with this problem... I have an I2C device (MCP23018) with a single pin to set one of 8 possible bus addresses. It does so by putting a 3-bit ADC behind the pin.
Well, what I actually want to do is control the address in this case using a DIP switch. So I figure I need to do a DAC conversion first to put voltage in at the right level.
Of course, everything I know about electronics, I know from searching the web or asking on this forum... So I found this: http://www.ikalogic.com/dac08.php
that seemed to do what I needed. It mentioned a R/2R resistor ladder, so I bought this: RGSD8L102G Datasheet
But that doesn't seem to do what I expect. Even before connecting the chip, I am just measuring the voltages at different dip settings. With a 4.98v voltage, I get these readings, which is nothing like what I would expect from a digital progression...
|1 & 2||3.168||63.4%|
|1 & 3||3.557||71.1%|
|2 & 3||3.735||74.7%|
|1 & 2 & 3||4.05||81%|
Also, switch 0 had no impact ever.