I'm interested in using the SC16IS740 UART-SPI converter to interface with W5500 Ethernet controller which has SPI inputs. Because the datasheet is unclear to me, I'm asking if anybody knows how is SC16IS740 programmed? By UART or SPI interface, or both?
If it uses the SPI interface for programming, can someone recommend a low cost UART-SPI bridge (or converter)?
W5500 is part of a data acquisition system composed of: several sensors boards with MSP432, each having a communication module which will transmit Ethernet over cable or fiber optic, and a "gateway" which aggregates all data from sensors boards and will connect to a local area network. W5500 will be placed at the gateway since
Some modules can transmit over Ethernet cable and other over fiber optic cables. The communication module is the Ethernet interface of the main board.
In case of transmitting over fiber, it has to convert electrical signals from W5500 to optical. Practically, I cannot place W5500 on the communication modules because it outputs 2 differential signals, thus requiring 4 fiber optic cables. So, a solution would be to transmit using UART (from main board to communication module and to gateway via fibers), thus using 2 fibers, and convert it to SPI (using SC16IS740) at the fiber-to-Ethernet converter, where W5500 would be placed. In this case, the master of SC16IS740 would be W5500, but is not acceptable.
Other solutions: transmit SPI data over fiber (unacceptable because it requires 3 fibers), use another controller to make UART-to-SPI translation.
Ideal case: placing on the communication module an Ethernet controller with outputs for fiber optic cables (I do not know any such controllers) and have and appropriate converter at the gateway.