Further Discussion on Software

As Nick discussed in his previous blog, we have been working on being able to operate all 4 DACs in such a manner that we can dim the LEDs as necessary using DACs 3 & 4, and be able to subtract out DC values using DACs 1 & 2. As of now, we have a program that allows us to run through the DACs, changing input values as necessary. In the near future, this program will need to be implemented in a manner where there is no longer a user defined interface, although that the computer will be programmed in such a way that it is making all of the necessary adjustments to our heart monitor signal through input coming from the ADC.

Problem statement #1: The ADC will take in an input signal, which will be analyzed. In the computer analysis, the signal will have an AC signal riding on a DC value. This exact DC value must be subtracted out, so that the signal sits on 0 V DC. This is important so that later in the system, the signal can be biased to 2.5 V allowing for the signal to swing in a dynamic range of 0-5 V. Build a program that allows the computer to calculate this DC value and is able to increment or decrement the DC value in order to have the signal sitting at 0 V DC.

Problem statement #2: As mentioned above, this signal will eventually be biased at 2.5 V. The signal then needs to use the PGA, or programmable gain amplifier to adjust it automatically to swing from 0-5 V, without having saturation.

Problem statement #3: Included above is our thoughts in having need for operating all 4 DACs and eventually operating them solely with the computer and no user input interface. This is another challenge to overcome.

Team Sierra is making progress in software situation, and most importantly identifying what the problems to overcome are. Before implementing ideas, it is important to explore the potential problems and come up with solutions to those problems. For example, it may be easy enough to identify a DC value from knowing the maximum and minimum values from peak to peak of our signal range. We would need to take a sample that would be inserted in an array to allow us to do this. However, we would also have to take into account where the minimum DC value starts from. We may find the DC value from peak to peak to be 1.5 V, although the minimum value may be sitting at 0.5 V to begin with. We must be careful for troublesome points such as this. In dealing with the gain, we must decide whether the computer program will be allowed to saturate before it decides that it needs to go back one gain setting. We must make careful adjustments to the PGA. All different scenarios must be considered.