communicationftdi
I want to create a USB to RS485 converter with auto switching between transmitting and receiving the data. I found this circuit schematic on the internet.
My question is,
Do we have to program EEPROM of the FT232RL before using it or I can directly mount it on the circuit
as shown in schematic and it will work?
in my circuit, 2 pin connector was used as RS485 connector and only A,B connecitons were made. (RI and ground connections were not used.)
RS485 proper wiring requires a common earth: -
You cannot expect disparate systems having their own ground connections to adequately handle the common mode noise that is normally present between separate grounds.
In addition the maxim document linked states: -
Although RS-485 can be successfully transmitted using multiple types of media, it should be used with wiring commonly called "twisted pair." What Is Twisted Pair, and Why Is It Used?
As its name implies, a twisted pair is simply a pair of wires of equal length and twisted together. Using an RS-485-compliant transmitter with twisted-pair wire reduces two major sources of problems for designers of high-speed long-distance networks: radiated EMI and received EMI.
I always use screened twisted pair with matching terminators.
You have not even attempted to use the 120R (across A and B) terminator.
The answer is right there in the very first screenshot - last Entry:
EEPROM Type: No EEPROM detected
So it seems your design either has no EEPROM connected to the FT4232H or they are not correctly connected or compatible. If they are missing you can glue one on top of the FT4232H and use flying wires to connect them - had to do this myself once because I thought I would not need the EEPROM for my design but I was wrong. So I had to add one afterwards.
Best Answer
Document ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf, page 33 says that CBUS2 - TXDEN (RS485 direction select)
Default configuration of CBUS2 – Transmit data enable for RS485 is enabled.
Check the pins used to enable the TXDEN.