I have a thermometer/hygrometer which directly connects a I2C EEPROM AT24C256 to a RS232 connector. The I2C protocol is spoken by bit-banging (see docs from here: https://oss.inqnet.at/trac/klimalogger/ ... umentation) the DSR (SCL) and CTS (SDA) lines. A request to takeover the I2C bus is sent via the TxD line (0x55).
That is the reason why a simple RS232 to USB adapter does not work as there is no serial protocol being spoken.
Because I'm not firm with electronics, the question is whether I can connect the 3 lines directly to the GPIO lines:
* DSR (SCL) -> GPIO 1 (SCL)
* CTS (SDA) -> GPIO 0 (SDA)
* TxD -> GPIO 14 (TxD)
My question is about the voltage levels. The thermometer is powered by 3 Micro Cells with 1.5 V each and I have measured 4V with my voltmeter. I just want to make sure that I will not brick my Raspberry Pi which has arrived yesterday after only 4 months
I have read the following section from the RPi Wiki:
"GPIO voltage levels are 3v3 and are not 5v tolerant. There is no over-voltage protection on the board - the intention is that people interested in serious interfacing will use an external board with buffers, level conversion and analog I/O rather than soldering directly onto the main board."