Verification

General Overview

For the hygrometer portion of the verification, we included two simulation outputs. Both demontrate the high level correct operation from the frequency determiner input, to the BCD outputs. Set 3 shows the correct operation of the keypad portion of the design.

Set 1

Set 1 shows the humidifier from powerup and reset, and going through a sequence of humidity values. The current humidity at time 0 was 39%. This is determined by using the timer formula f = 1/(22000 *C). We know f, so we can easily obtain C. Once C is obtained, we looked at the function graph provided on the Philips data sheet for our sensor to determine the humidity value. So, after reset, our frequency determiner started running, and finished at about 926500ns. Since this represents first sample taken after reset, the system latched this value no matter what. Eventually, the output in BCD came out correctly at 37%. The error is of coarse due to our linearizing of the capacitance vs. humidity function.

Once this humidity was determined, we manually changed the frequency of freq_in (from the humidity sensor), to represent a change in humidity of +1%. This should result in no change in any of the outputs from the chip, because changes or 1% are not recorded, as described in the frequency determiner section of this report. Thus, on page 3 of this simulation, where the frequency determiner is finsihed its task, we see no change occured in any of the output values.

We then proceeded to manually change the humidity again by a further +1%. We would expect this change to have appeared on our output this time, since a total change of +2% occured from the last sample. This is in fact what happened. The count from counter1 (the humidity counter) decreased by 2, representaing an increase in humidity of 2%. Thus, this new value was latched and the value progressed down the datapath. See page 4 of the simulation wave for more details.

We repeated the cycle one more time, as seen on pages 5 and 6 of simulation 1. A further change of +1% in humidity produced no change in the outputs (page 5), and an additional change of +1% was recorded in the outputs (page 6). This represents a total change of +4% from the beginning of the simulation, from 27% to 41% relative humidity.

Set 2

Since set 1 showed a humidity which turned the humidifier off, set 2 shows the determination and output of a humidity which turned the humidifier on. The default value for turning the humidifier on was set at 25%. Therefore, in set 1, the 'humid' signal was always off. In set 2, we adjusted the humidity to give a value of 10%. Since this is lower than the default 25%, the 'humid' signal went high, signifying that the humidifier turned on.

Set 3

This set shows the testing of input keypad values. Several sets of values were entered to test the operation of the humidifier controller signal, 'humid'. For example, on pages 1 and 2, the values were entered to set the desired humidity at 95%. After the keypresses, the output was correct showing 95 on the BCD signals 'keypad_msd' and 'keypad_lsd.' As well, notice that the signal 'humid' went high, due to the current humidity being 39%, and the desired humidity being 95%.

On page 4, 20 was entered on the keypad. This was output correctly in BCD. On page 5, the 'humid' signal went low, due to the desired level (20%) being less than the actual value (39%).

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