Going by the BCM2711 docs, DTR and DSR are not available through the UART implementation (only RTS and CTS, optionally). The traditional workaround for that is to simply wire those permanently high when connecting to a DCE (modem, or whatever) that needed those signals (and the same for a DTE which wants to see DCD), or just link them together at the DCE end. For most practical purposes, you don't normally need DTR & DSR as active signals, just sometimes need them asserted to keep a device happy; RTS & CTS alone are sufficient for flow control. If neither end of the link cares about DTR/DSR and DCD, just ignore them completely. If you really need to use DTR & DSR for something, as active signals, it's probably possible via GPIO. If you do need flow control, RTS/CTS is usually preferrable to XON/XOFF.You will be able to get away with just a three wire RS232 (TX, RX and Gnd).
As for the hardware handshaking signals (RTS, CTS, DTR and DSR), if I recall correctly, just connect RTS to CTS and connect DTR to DSR. Doing so will fool the side requiring the hardware handshaking.
Statistics: Posted by Murph9000 — Wed Aug 14, 2024 1:06 pm
