Rev2 aka, "What do you mean RX doesn't go to RX and TX doesn't go to TX?"

A project log for ESP32 pico dev board

Practice project using ESP32 pico. Has USB, charge circuitry, 6-degree accelerometer, a button and some LEDs

morganmorgan 11/15/2018 at 22:193 Comments

I don't know how many times I've done it. But I'm sure I'll do it again. Some dyslexic holdover from childhood where I cannot get it straight.

TX connects to RX. RX connects to TX.

Okay! Schematic is updated, besides the obvious fixing TX/RX I also decided to ditch the test pads. As much as I'd like to be making test jigs I just don't have time. So instead I added a 12 pin header and broke out a bunch of important signals.

The top is pretty clean; UART, Power, Reset, Bootload

The last 4 are the GPIOs for the LEDs, I'm questioning if I need DTR/RTS. Maybe the button is more useful...

Anyhow. Another update on the layout coming shortly.


alan_r_cam wrote 11/16/2018 at 03:53 point

It's not Rx to Rx that's confusing you - it's DCE vs DTE.

DTE [Data Terminating Equipment] is the PC, DCE [Data Comms Equipment] is the modem, radio, or whatever.  Traditionally, data goes: 

DTE Tx  -> DCE Tx -> comms meduim -> DCE Rx -> DTE Rx.

Problems happen when you junk the DCE's and make a null modem crossover cable. THEN the Tx of one DTE goes to Rx of other DTE. In RS232 serial, you also cross the RTS / CTS control signals.

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Jarrett wrote 11/16/2018 at 01:03 point

A trick I've started doing is adding termination resistors for TX and RX, right next to each other.

You really should be anyway for fast signals, but this way, when you mix up TX/RX (which I swear happens, like, more than 50%), you can bodge the 0603 resistor pads to fix it.

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morgan wrote 11/16/2018 at 01:26 point

Good tip! I'll give that a try. (because ya know, I'm not going to stop making this mistake)

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