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12/11/2019

Can you use an ESP32-CAM module like a standard ESP32?

I've recently been experimenting with detecting if my flat is occupied using Bluetooth Low Energy (BLE) Trackers attached to my wife and I's keys in order to trigger various smart home "scenes". There's been trials and tribulations, but after trying various methods I've managed to get arrival detection down to pretty much instantaneous, and detecting someone leaving to below than 60 seconds, which I'm pretty happy with. After initially trying to do the detection with a Raspberry Pi, I quickly moved onto to an ESP32 based solution as the software on the Pi would frequently crash.

One thing I discovered fairly early on was now and then a BLE tracker would "disappear" for a brief period, usually a minute or two. I wasn't able to figure out the cause but put it down to interference or a collision, but the work around was to have multiple ESP32s receiving the beacons and aggregate the results. For my modest flat I'm currently using 3, although I could probably get away with 2.

A recent update to the ESPHome BLE Tracker has significantly reduced these disappearances but they still happen now and then. In a bid to eliminate them all together, I started to wonder if an external antenna would improve reliability. After looking around online it became apparent only a small number of ESP32 dev modules had an antenna connector, and they were hard to come by and fairly expensive.

But wait... what are these ESP32-CAM things? They're cheap, readily available and have an antenna connector which can be selected by switching the 0 ohm resistor to the second position. I bought one without doing much research (obviously) and it turned up last week.

ESP32-CAM Module
Anyway, I digress. I should really cover the BLE detection in another blog post so watch this space. If you want to find out if the ESP32-CAM can be used like a standard ESP32, click read more...


So, back to the ESP32-CAM... It's a small module supplied with a small camera, an SD card slot and a bright "Flash" LED. Numerous firmwares are available that allow you to use it as a webcam or CCTV camera, but looking at various Youtube videos and reviews the results don't look mind blowing. Maybe I'll give it a try sometime but that's not what I've bought it.

It has less pins then a standard ESP32 dev module, 16 vs 32+, and doesn't have a USB connector for power or programming. It does have voltage regulator to drop 5V down to 3.3V, and most modules have a IPEX connector for an external WiFi / Bluetooth Antenna.
ESP32-CAM Pinout

So the first step was to try and load ESPHome onto the module. I won't cover it here, but I hooked up a USB to UART converter and used esphomeflasher to upload the binary. It didn't work first time - I'd forgotten to pull GPIO0 to ground as it booted. The second time I got lucky and managed to flash the ESP32, but it was failing to boot properly. Turns out my USB to UART converter couldn't supply enough current (~150mA) so as soon as the WiFi initialised it rebooted. I hooked it up to an external power supply and success, the ESP32 booted and started playing ball.

At this point I'd established that the ESP32-CAM can indeed be used in place of a "standard" ESP32 Dev Module, and Wifi and Bluetooth works as expected. But what about adding additional peripherals? At this stage I didn't know if all the pins are already in use for the additional camera hardware, but after a little experimentation I've managed to get an i2c current sensor and a DS18B20 temperature sensor working with the module.

I've documented how I used the available pins below. It may be possible to use some of the others, but these are the ones I've tried and tested:


Pin Usage
33 Small on board LED
4 Larger "Flash" LED
14 SDA
15 SCL
13 Dallas 1-Wire
12 Failed to boot with anything connected!

So, I now have a cheap ESP32 module with an external antenna, Bluetooth presence detection, as well as support for any i2c peripherals and a temperature sensor. Not bad.

So, Tl;Dr: Yes, you can use an ESP32-CAM as a standard ESP32, with some limitations.

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