Which serial pins do you use? Some use only RX+TX, some use RX+CTS+TX+RTS, some use all: RX+CTS+RI+DSR+DCD+TX+RTR+DTR.
I think the OP might be referring to
TI MAX232DR, which works from a single 5V supply, uses four 1µF capacitors (I'd use 50V rated X7R because I'm a hobbyist and the datasheet says they're acceptable), can do 115200 baud, and supports two incoming and two outgoing signals, for example RX+CTS+TX+RTS or RX+DSR+TX+RTR, depending on how your 5V device does hardware flow control (if at all). Mouser sells these for
0.62€ in singles, with for example MaxLinear
SP232EEN a pin-compatible device.
These will work, as long as OP only needs at most two incoming and at most two outgoing serial signals on the 5V device. The datasheet above shows how the chip is used, but you can find MAX232DR-based break-out boards with RS-232 connectors on them, too. It is very common to only use RX+TX, but I personally find that hardware flow control makes life easier, so I do like to use that myself.
Just note that buying the MAX232DR chips or break-out boards from
random sellers from eBay or Aliexpress can get you garbage. Pick a seller who has sold lots. These are not expensive at all, so no reason to pay more than about $2 each.
If you only need RX+TX, then
TI MAX3232 is often considered superior, because it supports higher baud rates, and works from 3V to 5.5V. The
Seeed Studio RS-232 adapters are generally considered good, and you only need to connect four wires (your logic voltage between 3V and 5.5V, ground, RX, and TX), but again, there are all sorts of fakes around there. Clones are usually okay –– you'll find the schematic is the same as in the TI datasheet ––, it's the fakes with fake ICs that you need to avoid.
Note that in any case, this assumes that your computer's RS-232 is referenced to the same ground as your 5V circuit. Otherwise, you need
isolation, not just voltage level translation.
Home
Help
Search
Login
Register
