PCB Layout Design Schematic Capture Autorouting Software. Quick links for PCB design, schematic capture, routing, spice simulation software. New in ExpressPCB 7. Production 10 day build option is now 5 day build. Promotion Code option is now available in the order process. Microfit 5 With Crack'>Microfit 5 With Crack. Read the full. Welcome to my collection of Amateur Radio Projects. I do a lot of portable operating and prefer lightweight directional antennas such as the Moxon Rectangle. Now the simple fulladder logic circuits can be combined to allow bigger binary numbers to be added together. This picture shows a four bit adder, in fact, due to the. The screen capture of the ExpressPCB version of my PICkit 2 clone I call PK2 is shown above. Below are the PCB layout and Schematic for the board. Real Time Audio Spectrum Analyser Waiting for Friday. This project implements a real time audio spectrum analyser using a PIC1. F4. 55. 0 8 bit microcontroller. The spectrum frequency analysis is performed by a highly optimised 1. Fast Fourier Transformation FFT routine coded entirely in C. The output from the FFT is displayed using a 1. FHO/ERGT/FCZERDXJ/FHOERGTFCZERDXJ.MEDIUM.jpg' alt='Expresspcb Full' title='Expresspcb Full' />A list of free PCBPrinted Circuit Board design software which facilitates easy pcb layout drawing. List has open source, free download design tools. ExpressPCB circuit board layout program is a snap to learn and use. Laying out PCBs is easy, even for the first time user. Here are the steps First downlo. SShotExpressSCH_1.gif' alt='Expresspcb Full' title='Expresspcb Full' />LCD to allow a real time view of an audio signal. RTSA running. You. Tube Demonstration Video. Hardware. In order to perform a FFT calculation on an audio signal it is necessary to prepare the audio so the PIC1. F4. 55. 0 can sample the signal. The PIC1. 8F4. 55. ADCs which can be used to measure a voltage from 0. V to 5. V with 1. A typical audio line out signal is an analogue wave with a peak to peak intensity of 2. V centred around 0. V i. e. it is an AC signal ranging from 1 to 1. V as shown by the following oscilloscope trace from pin W2 of the demo board W2 5. Hz 1. VThe picture shows a full volume 5. Hz sine wave generated by a PC. If we were to feed this signal directly to the PIC we would only have a very small range of input voltage 0 0. V and also we would only be able to sample the top half of the signal which would make the FFT incorrect. In order to correctly sample the signal we have to do two things. Firstly we need to amplify the signal to ensure we can use as much of the 0 5. V range as possible. Secondly we have to move the signals ground of 0 volts to a virtual ground of 2. Vs. This will allow the PIC to sample both the positive and the negative sides of the input signal. To do this the demonstration board uses a simple amplifier IC the LM3. Since the IC is powered from a 0. V and 5. V power supply it has the handy side effect of also moving the signal into the middle of our required power range. The LM3. 86 1 was used because it is cheap and simple, however you could use a rail to rail opamp to achieve the same thing with a few more external components. The following oscilloscope trace shows the output signal from the LM3. W3 of the demo board W3 5. Hz 5. VThe hardware mixes the stereo line in using two 1. K resistors which act as a simple mixer. The signal is then passed to the LM3. K potentiometer which allows the signal strength to be adjusted. Next the LM3. 86 1 amplifier output is passed through a simple RC Filter which rolls off the signal at about 1. Khz. The resulting signal is then fed into an ADC pin on the PIC1. F4. 55. 0. The 1. Khz filter acts as an anti aliasing filter for the FFT which cannot correctly detect signals with a frequency of greater than 1. KHz. An RC filter is a very simple type of filter and very ineffective but it was chosen since it is easy to build and only requires 2 passive components. Typically a professional spectrum analyser would implement the anti alias filter at 8. Nyquist frequency for the FFT see below, but since we are so speed limited with the PIC this is not possible to do in the design. The demo board also controls a standard 1. LCD as well as 3 LEDs for testing sound to light conversion. In addition there are 2 switches to allow the user to control the LCDs output depending on what is being measured and how it is to be displayed. The second phono socket allows you to pass through the input signal to another audio device such as headphones or speakers. Here is the circuit schematic for the demonstration board Real time Spectrum Analyser schematic. The circuit board design is a single layer PCB using only through hole components to make it as easy as possible to duplicate. I used a PIC1. 8F4. IO pins however it can be directly replaced with the smaller PIC1. F2. 55. 0 which is code compatible. The circuit is also simple enough to be built easily on a breadboard if you wish to experiment with the design. Here is a picture of the PCB artwork which is included in the downloads section below RTSA PCB artwork. Firmware. The firmware is completely written in C and can be downloaded from the downloads section below. The firmware is split into 4 parts ADC Sampling. The ADC sampling routine samples the voltage level on RA0 every 5. S. This gives us a sampling rate of 2. Khz 2. 0,0. 00 times a second. It is important for the FFT that the samples are evenly and accurately placed. To ensure this there is a small delay in the sampling loop which is calibrated using an oscilloscope on the W4 pin of the demo board. The total duty cycle of the square wave on W4 should be exactly 5. S. The ADC is sampled at the full 1. This means that the resulting samples are in the range of 5. FFT mathematics requires. The ADC sampling routing takes a little over 6. S 3. 2 m. S 3. S in execution time for each loop. FFTThe FFT routine was taken from an example found on the web references to the original code can be found in the source code. FFT maths is complex and I dont pretend to fully understand itThe code was stripped down to the minimum required commands and ported over to the PIC1. F. Since the PIC1. F4. 55. 0 has a hardware 88 multiplication function within the processors ALU I also optimised the calculations to allow the compiler to correctly use the chips capabilities. The fact that the 1. F has a 88 hardware multiplier is really the key to how such a low power chip can perform real time FFT. The cycle speed advantage even with 1. Absolute value calculation. The output from the FFT is 3. FFTs via Google if you want to know more. In order to show the result in a meaningful way it is necessary to calculate the absolute value of the complex number which is done using a Pythagoras calculation to calculate the complex numbers distance from the origin of 0. This involves performing square root operations on the numbers so the software implements a very fast integer based SQRT equivalent since any floating point operations would be way too slow. The FFT routine and the absolute value calculations combined take approximately 7. S 7. 00. 0 u. S for each loop. Updating the LCDThe 1. LCD has to be updated as fast as possible. Rn To Paramedic Program In Ohio. To do this I used a very simple bar graph drawing algorithm which requires the minimum possible number of commands to the display. The routine takes advantage of the way the LCD display is addressed in order to make the update as fast as possible. The two switches on the PCB allow the user to switch between x. B. These are simply different ways of showing the output depending on if you want accurate frequency level representations, or more eye candy based output The LCD update routine takes approximately 4. S for each update. Overall FFT speed. The approximate speed of the spectrum analysis display is one frame per 1. S resulting in an overall frame rate of about 6. FPS without the LCD. This can be easily improved by either reducing the required number of frequency buckets which would reduce both the sampling and FFT execution times or by using a display device with a faster update time. If you wished to use the FFT to control LEDs for a colour organ you could quite easily do both. Frequency buckets. The FFTs Nyquist frequency the highest frequency it can detect is 1. Khz. The 3. 2 frequency buckets are split evenly over the range, however, due to the way the FFT routine works you cannot use the lowest bucket. This means the displayed frequency for each bucket is as follows in Hz 1 3. Conclusions. Ive no doubt that both the software and the hardware can be improved. Im no expert in FFT but I would love to hear any ideas on how to get it going even faster.