ESP8266 Community Forum

Rural wrote:the ESP-01 only exposed a single GPIO pin. In fact, it exposes three.

@Rural, where did you see that said ESP-01 has 3 GPIO? I thought it was only 2. Could not see that on either of your links, might have missed it.

I am having some serious problems with my ESP-01 at the moment, it won't run any sketches at all. But it worked before and worked great. Once I get it working again...

Anyway, as already mentioned, you can use many i2c devices with ESP-01, like temp/humidity/pressure sensors, I/O extenders, ADC extenders and so on. I plan to experiment with ATtiny85 and/or ATtiny84 as slave i2c devices. This would give a few extra analog/digital inputs/outputs if that is all that is required, and allow monitoring of inputs while the ESP is in deep sleep to save battery power. For example, I plan to measure wind speed & direction using some inexpensive sensors connected to an ATtiny, which can do this on minimal power. Every few minutes, I plan to have the ATtiny wake the ESP via the CH_PD pin. The ESP will then read the ATtiny's results over i2c bus, plus other i2c sensors, connect to wifi and send the results to a server.

If you're not going to use the UART, you can actually use 4 GPIO's. Otherwise it's 2 (with restrictions: pull up obligatory and you appliance must be tolerant against the garbage during startup).

lethe wrote:Desoldering single pins is much easier, just cut the plastic to seperate the pins before desoldering. Then heat the pins, pull them out and use some solder wick to clear the pin holes.

Good tip. To be honest, that's what I've ended up doing in the past...kind of. I was lucky enough that the plastic holding the pins had a low melting point. So when the solder let go, so did the plastic. I was able to pull the pins out one at a time.

eriksl wrote:If you're not going to use the UART, you can actually use 4 GPIO's. Otherwise it's 2 (with restrictions: pull up obligatory and you appliance must be tolerant against the garbage during startup).

Cool. This platform looks a bit less user-friendly than the Arduinos I'm used to, but...$2.58 and wifi?!? That's worth the trouble.

Most of my Arduino projects use one or two simple sensors (usually just temperature), an NRF24L01+ transceiver, a few buttons and an OLED screen for an interface. Sometimes the device controls a couple of MOSFETs (usually via PWM) or relays. Wifi would allow me to move the interface to HTTP and ditch the buttons and screen.

I do remote control cars as well, but usually skid steer. A simple car controlled over wifi seems like a good project but a single PWM output probably limits it. [Edit: Actually, there is a single ADC input on the ESP8266, but it seems like most of the GPIO pins can be configured as PWM outputs.* If that is the case, I'm a very happy camper.]

[* Neil Kolban's The ESP8266 Book, page 95.]