Re: Circuit Analysis of Easy I2C Programming Circuit
Date: April 07, 2015 04:16PM
here are the answers for your questions:
1. The two transistors connected to LPT connector on pin 2 and pin 3 are used only by the "data" transmission from pc to the i2c device connected via easyI2Cbus interface. And yes, they are both inverted.
2. & 3. For receiving data (from i2c device to PC) are only used LPT pin 12 and pin 13. The transistors are in this direction unused.
Every communication is fully controlled by software - PonyProg2000. The output data is "created" by generating voltage levels (log.0 = 0V and log.1 = 5V) for driving external transistors (pin 2, pin 3). Reading the input "data" (voltage levels at LPT pins 12 and 13) at the time defined by the communication protocol is controlled by software as well. So if you choose in PonyProg2000 on the interface setup dialog the correct interface type, the software automatically makes needed settings (e.g. inverted/not inverted signals) internally.
Communication ports COM and LPT are used by the PonyProg2000 ONLY as a PC input / output interfaces with direct access to their pins. There is no standard data flow, so in this case is the meaning of pin descriptions more or less irrelevant.
> I am going to use the circuit shown in below link
> for programming 24Cxx series EEPROM device. I have
> few queries regarding the analysis of the
> Circuit Link :
> Queries :
> 1. The D0 (Pin 2) and D1 (Pin 3) of Parallel port
> are connected to SDA and SCL of EEPROM through
> Transistor. I understand that this connection is
> done to provide open collector driver. But whether
> this results in inversion of DATA and CLOCK
> 2. The I2C Data line is bi-directional. When DATA
> is Input to LPT (driven by EEPROM), how the data
> transmission happens in spite of the Transistor
> 3. Why SDA and SCL are connected to Pin 12
> (PAPER_OUT) and 13 (SELECT) of Parallel port?
> Please clarify these queries before we start
> assembling the circuit.