rickyjar
Member level 2
User “Kabelek” presents his USB adapter on RS232, RS232 with the levels TTL, I2C and 3-Wire with an automatic signalization of conditions on pins.
The construction is not advanced but practical. The main circuit is FT232RL that converts USB signals into RS232 with the levels TTL. Next, the RS signals are switched with 3 74HC244 circuits. The first one transfers the signals to the converter from the level of TTL to the level of RS232 signals built on the SP3243 circuit and further to the socket RS232 DB9M.
The second 74HC244 circuit transfers the TTL signals directly to the socket RS232 TTL DB9F. Two different sockets (female and male) were used on purpose to avoid an accidental incorrect connection of cables.
The third 74HC244 circuit transfers the signals to the I2C and 3-Wire adapters. The I2C adapter itself is a typical known adapter according to the datasheet of Siemens, only connected to RS instead of LPT and with an additional line DLEN/DO, which offers the possibility to control the 3-Wire mains. Next, the I2C signals are transferred to the Jack sockets and mini DIN socket. The DLEN/DO signal and +5V power supply is additionally connected to the mini DIN socket, which offers a double function of this socket as a I2C and 3-Wire and possibility to supply power to any small circuit or memory. The programmed power consumption on USB in FT232RL amounts to 500mA
A selection of an active output is made with two switches.
I2C or RS is selected with the first one, and RS with the TTL or RS232 levels is selected.
LED diodes signalizing conditions on the I2C/3-Wire mains, operates only in the case of active I2C/3-Wire outputs. The remaining ones operate in each case, but the diodes signalizing condition of the signals on the output with the level of RS232 are a negation of the signals from the TTL output.
The very part of the adapter is made to be in accordance with the user’s own written program, so it is not known, if it is compatible with other similar devices. Although there are some diagrams of a RS232 attachment on I2C, but without a DLEN/DO line, only SCL, SDA, on the Internet, but it was not checked, with which programs they cooperate.
Some pictures:
Link to original thread - Adapter USB na RS232/TTL/I2C