Programming I2C Serial EEPROM 24CXX

[jorgemoreno]

Hi,

I am experimenting with a programmer for 24CXX type serial EEPROMs, I developed a programmer interface for the serial port (I don't want to use the parallel port which is a common preference) on the PC, I have tested this programmer using PONYPRO program and works just fine, the thing is that just to better understand how this type of devices work I want to develop my own application using Visual Basic and the MSCOMM control. The data sheet of a 24CXX suggest that for a READ the following sequence must be done:

START 1010AAA0 N HHHHHHHH N LLLLLLLL N START 1010AAA1 N
210 76543210 76543210 76543210
RRRRRRRR N STOP

where R indicates the PC reading a bit.

Frankly, I know how to send or recive data on Visual Basing through the MSCOMM, but I don't know how to control it to send such a sequence described before in which a for instance to make a SATRT condition you must make a transition from High to Low of SDA while SCL is High.

So if someone has experimented using Visual Basic/MSCOMM and the Pc'Serial Port to program a 24CXX please giev a hint.

The circuit is below just try to make it look right by copying and pasting it on a notepad document.

Thank you very much-

100n| |
--| |--
| | | | PC SIDE
| | LM7805 SERIAL PORT
24CXX | \ / ---------- 1N4148 RS232
---------- | | | | /| -
--|A0 VCC|------------|Vout Vin|----------------------|< |---------|4| DB9 - DTR
| | |jumper | | GND | | | | | \| | -
--|A1 WP |-o o- |+ ---------- + | | | |
| | | J1 | --- | --- --- | |
--|A2 SCL|---- | --- \ / --- --- | | /| | -
| | | | | |47u 47u|___|100n ---|< |-----|---|6| DB9 - DSR
--|GND SDA|-- | --| | | \| | | | -
| ---------- | | \ / \ / | | |
\ / | | | | | -
| | | | -|7| DB9 - RTS
| | 4.7K | | -
| ---------------------/\/\/\-------------------- |
| | |
| | 4.7K |
|-----------------| -----/\/\/\----------------------
| | |
| | ---´
| ---´ ´ ^ -
| ´ ^ /___\ ---|5| DB9 - GND
| /___\ |4.7V | -
| |4.7V | |
| | | |
| \ / \ / \ /
|
| -
--------------------------------------------------------|8| DB9 - CTS
-

 

[felixc]

Your drawing is unreadable on my computer.
Can you use MSCOMM to set the control bits individually? You more or less need to drive these bits as a parallel port.

Are there any utilities in VB to drive the printer port? It might be easier. The levels are already at 5 volts, and they are open collector.