I need to convert, linearly, a voltage in the range of about 1v to 2v into the range 0 to 1v for input to an ADC.
This is the background: I fiddle with electronics and programming as a hobby to give me interesting and challenging projects -- but on this one I am stumped.
I have built a power supply to give me 0 to 1 amp, approx, and want to add an ammeter to it. I will use a Sparkfun ACS712 Low Current Sensor Breakout board which I can adjust to give a voltage output range from 1.000 to 2.024 volts over the input range of 0 - 1024 mA, so that a 10 bit ADC with these as its lower and upper reference voltages will give me a nice 1mV per mA per bit output. I will be happy with a 1% or so accuracy.
I intend, if I can, to use a Microchip PIC12F675 to do this conversion, but it allows adjustment of only the upper reference value. To display the current reading I will use an I2C link to a Sparkfun 7-Segment Serial Display COM-11442.
So my question is: please, how do I convert the 1.000 to 2.024 voltage range into 0.000 to 1.024 to suit the ADC?
As an alternative, is there a different small PIC that I could use, which has an ADC with a variable lower Vref to a 10 bit ADC, and also an I2C serial module? I have looked on Microchip's website, but the needle, if it is there, is in a bewilderingly impenetrable haystack of data.
I want to use a PIC because I can program them easily in Assembler, which is a process I view with somewhere between enjoyment and love, and I have the software and hardware to do it.
This is a specific question, please don't suggest other ways I can sample the current, I can do that myself. Thank you.