This is a Test Circuit for Logic Analyzer software, with the Simple port circuit. The VB Logic Analyzer works, but is just an example program to test and learn.
The speed at which the logic state changes say like 10 M Hz while probing even a PIC or 89C51, is too fast for this circuit. For that, the incoming data has to be spooled or stored in RAM at real time, by the external Hardware itself.
Test Circuit for Logic Analyzer software – del20006
As this is a Parallel Port Interface, an Embedded High Speed Digital RAM Storage of Multiple Logic input Channels with Signal Conditioning in the front end, could do the job. This is the minimum, if you want to program the rest of the instrument on Computer Software. Here is one you can see from Bitscope using USB or Ethernet.
Printer Port Circuit to see the inputs logic state and drive a few outputs. The preset control program helps test out the circuit operation. Use safe 5V Levels.
Simple Printer Port Interface, Input-Output – del20005
So i made some example circuits and VB programs for students. A demo Milli Volt source, Digital Voltmeter and Logic Analyzer examples for learning, are on these pages. I have tried to derive power from PC itself in this circuit, Care should be taken not to short circuit or apply any voltages above 5V to PC Port Pins.
74HCT373 is the only chip used to interface the real world with the PC Parallel port. The Inputs to this chip are protected with Resistors and Zeners. 3 outputs of PC are also monitored using LEDs. This gives you a IO interface for experimenting. Below is a Preset counter simulation that you can use with this circuit for testing. Schmitt Triggers and Signal Conditioning may be required for Noisy and Non-Sandard Inputs.
This circuit uses a R-2R Ladder Resistor Network to convert digital data from PC Printer Port to Analog. This can be used as a Millivolt Source or Programmable Power Supply.
This circuit is a R-2R, Digital to Analog Converter. You can replace the R2R with a D-A Chip for better performance. This circuit is just to understand the Concept, for learning and Experimenting.
Milli Volt Source for Printer Port
The MFR resistors are 1%, hence the precision of this Conversion is not very good. It is ok for servo applications or closed loop conversion along with the ICL7135. That can be tried with software.
A 4053 Analog Switch controlled by PC software will give you a negative or positive output. R41 trimpot is to calibrate or scale output. If you modify this circuit, you could output data at a fast rate, then you have a staircase generator. You can write software for a waveform generator or function generator too.
You can design a dual tracking power supply over this. You can loop it with the DVM circuit shown earlier and make a 12 bit accuracy millivolt or milliamp source. It will depend more on the software and little addons to circuit.
This is the standard configuration on how to Interface a uC like 8051 to PC RS232 with MAX232A. The UART or Serial port was not present in 8049/8749 chips which were the ancestors of 8051/8031. Pages of code were needed to make a software UART in MCS-48. The 8051 integrated the hardware UART and short commands made it tick. The most important innovation which made uC popular was the C in 80C31. C is for CMOS. This made the chip work cooler and work on even batteries and small power supplies.
80C51, SBC, Firmware and Circuits
The 8749 and 8751 are the UV EPROM type of uC. With limited erase/write cycles. The FLASH revolution changed every thing, you could update firmware over a phone line modem. Even without Ethernet, the firmware could be updated by making every embedded device a node on the EPABX. Now TCP/IP and Wi-Fi makes it all very easy.
Read also –
A PC based Analog Voltmeter. The Printer Port or Parallel Port Interface is used to acquire high resolution analog data using ICL7135. This is a method of getting analog data into your PC. This is only of Educational Value. Applications include Data Loggers and PC based Process Monitors, chart recorders. (USB, Wireless Interfaces and Tablet Computers are in vogue today
ICL7135 to Printer port Interface
The four Digit Drive outputs and four BCD outputs of the Multiplexed Display Driver of 7135, along with A-D status output which is also four, are routed to four input pins on printer port via three 74HCT373 Digital Switches. This is because we have less Input pins on Port and 4 are shared by making one 74HCT373 transparent and others High Impedance when PC takes a reading. So the three sets of four outputs of 7135 can be read sequentially.
74HCT139 U9A which is controlled by the PC program can select U3, U4 or U5 for sending data to 4 pins on printer port. Data sent on the eight output pins of printer port can be latched by U10B into U6. This eight outputs of U6 can drive relays or lamps.
The ICL7135 details can be seen here 41/2 A/D with BCD ICL7135 . This Mixed device was far ahead of its times, a product of Intersil.
Using this circuit on Printer Port, one could drive 256 Relays or 16K LEDs as Dot Matrix display. It can be used to drive a Large size multiplexed LED dot matrix display or Latched Relay-Solenoid-Motor-Lamp Array Drivers.
This circuit can be modified for a Static drive output or a fast changing output like a Waveform Generator. You can also make it a 16 Bit waveform generator. The frequency limited to the speed of the port or a fraction of it, depending on 8bit, 16bit or 32bit.
Now I have Some Explaining to do. Latch the U7 with a 8 Bit Data to address the device you want to talk to. So one among the 32 Output Devices can be Selected by a combination of G1-G2 of U5-U8 and U7 8 Bits, Split into Two Nibbles for Upper and Lower 16 Devices. That means 16 * 2 = 32 Devices of 1 Byte each,. 32 * 8 = 256 if my calculations are correct. Please verify.
One of the decoders U5 or U8 decode their respective nibble and output a Low on Selected device to Latch Data on the Chosen one (74HCT373). Why HCT ? Speed is good, low power and CMOS ! and works with TTL too. It Interfaced well for me on a Card with Both TTL and CMOS levels, with a Fast uC.
The 74HCT373 outputs are current amplified and isolated by darlingtons and optoisolators. Both source and sink examples shown. This circuit was not tested and documented properly. So there may be things missing. It is just a Concept design..
Printer Port 256 Relays 16K Dot Matrix – del20021