I'm trying to use an ESP07 to take AT-command instructions from an MSP430F2274 microcontroller through the UART Rx line. The MSP430 is currently configured to send "AT\r\n" about every second at 9600 Baud. My breadboard basically looks as follows:
Incase the picture doesn't load, all my connections are as follows:
For the ESP8266:
VCC -> 3.3V
GND -> ground
EN -> 3.3V
GPIO0 -> 12K resistor -> 3.3V
GPIO2 -> 12K resistor -> 3.3V
GPIO15 -> 12K resistor -> ground
Rx -> MSP430 Tx
Tx -> MSP430 Rx
For the MSP430:
VCC -> 3.3V
GND -> ground
Rx -> ESP07 Tx
Tx -> ESP07 Rx
What I am expecting to see is Channel 1 of my oscilloscope (MSP430's Tx / ESP07's Rx line) to show a pulse each time the "AT\r\n" is sent, then some pulses on Channel 2 (ESP07's Tx / MSP430's Rx) in response, which would presumably be the "OK" (or possibly some error message).
When I turn on the power supply in this setup, the ESP07 Red LED comes on (no Blue LED blink), and the oscilloscope shows Channel 1 going up to 3.3V then pulsing down to 0V quick, which is the "AT\r\n" coming through. Channel 2 (ESP07's Tx / MSP430's Rx) shows 0V.
Interestingly, if I disconnect both the Tx and Rx line from the MSP430 and power up, the Red LED still comes on, but also Channel 1 shows a quick pulse before going to 3.3V, Channel 2 pulses up and down for about a second before going to 3.3V (with Blue LED flashing for this duration), then both lines stay around 3.3V with some 250mV downward pulses on both constantly coming (at a somewhat regular period of ~100ms), no further Blue LED flashing. Obviously there's no pulse to 0V on Channel 1 as there was previously since the MSP430 Tx has been disconnected.
If I only attach the MSP430's Tx (so Rx is disconnected), I get a combination of these two: both channels follow what happened in the second scenario and pulse as mentioned before getting to 3.3V, Blue LED blinking included, after which Channel 1 shows downward pulses to 0V at the ~1s interval along with the small 250mV ones, while Channel 2 just continues to show the 250mV pulses.
If I power on with neither Tx nor Rx from the MSP430 attached (like the second scenario) but then add the MSP430's Tx, I get the same as I did in the paragraph above this (the third scenario). If I add the MSP430's Rx to this, Channel 2 (ESP07's Tx line) shows a very small dip of about 200mV but then continues on no differently.
I have also tried using a different ESP07 and got the exact same results. I flashed an ESP-12E module on a NodeMCU breakout board to accept AT commands and hooked it up with simply Rx/Tx connected with the MSP430, put them to the same ground, and saw on the oscilloscope the pulse of the AT sending along with the echo then response from the ESP-12E on Channel 2. I'm pretty sure this is generally what I'm looking for in terms of response from the ESP07, but I'm not getting it.
Does anyone have any ideas? Thoughts I've had are:
-It's a power issue (though Red LED is always on)
-GPIO setup is wrong
-EN needs to be put through a resistor before being tied high (read this somewhere I think, does it matter?)
Many thanks in advance, sorry for the long explanations.