Hardware

My Favoured ESP modules

This is not intended as a comprehensive hardware device review, just a mention of some of the hardware I find useful, and why. Top of my list is the Serial Dev Kit ESP-202 module - thankfully I bought several while they were available, because they are now harder to find.

Some of the useful features are:

On/Off switch ... sounds obvious, but I don't know any others with one.

Easily accessible GPIO0 jumper ... offering push-on switch replacement.

RGB LED connected to gpio's 12, 15, 13.

Onboard status LEDs for gpio's 16, 14, 2, 0, 4, 5 and power-on.

The RGB LED and onboard status LEDs allow easy monitoring of gpio pins without requiring external LEDS and limiting resistors.

Top-mounted breakout pins.

On-board USB UART ... my normal method of powering the module, even when portable from a USB solar power bank.

Onboard switchable ESP-01 socket ... allows plugging in ESP-01's for testing, programming, flashing.

Battery box supplied ... but rather than soldering it directly to the module, I solder pins to the module and connect dupont female sockets to the box.

This allows the battery box to be plugged on if needed, or a Lipo instead, or it makes available a pin from the USB 5v to power external 5v devices. All usable ESP pins are broken out, which now includes 3.3v and 5v pins plus 3 GNDs which are available for connecting to external modules.Replacing the gpio0 jumper with a momentary pushbutton offers convenient one-handed operation with the On/Off switch for booting up into flashing mode, and is also useful for adding other types of user switch.

Second favourite is a "Next Evo" produced by TrackerJ, It has the autoflash feature similar to NodeMCU but it is slimmer and therefore more breadboard friendly. Plus the pin holes are left vacant, so it can be fitted with 'arduino-style' long pin header sockets if wished. But... what makes this module really useful for me, is the provision for fitting an i2c header socket. Look at the bottom one shown in the picture and you can see a PCF8591 AD/DA module plugged in and standing up vertically - giving 4 analog inputs (connected to a trimpot, LDR & thermistor) plus a digital to analog converter... and all without any wires. This offers the easiest way for i2c development that I know of. I bought a couple via email, and when I mentioned the difficulty of finding or ordering them online TrackerJ said that his sales are normally from 'walk-in' customers, so I don't know if they will be available online.

Another useful dev 'special' is a single-inline module bought from a Greek ebay seller a couple of years ago.

It plugs upright into a breadboard, giving a very narrow footprint, allowing more room for other components.

You can see one plugged into the breadboard, and another leaning upside down against the bottom edge.

All the normal pins are available in a single row for plugging into a breadboard or female header socket.

The UART connections are separate and opposite.

The guy making them was also advertising them elsewhere, so they may still show up in an online search.

I'm not a fan of the relatively chunky NodeMCU, but the version with integral OLED offers a handy self-contained on-screen display for output.

The Wemos D1 Mini is the NodeMCU baby brother with a more practical footprint and offering a range of plug-on shields, even an OLED display. A nice feature of NodeMCU and Wemos devices is their easy 'autoflash' capability which avoids having to ground gpio0 during reset for flashing.

In practice that's not so important because even 1M Baby Basic devices only need flashing in the first instance, then can be kept updated by OTA.

I have various other ESP modules which I don't bother developing with because they don't offer me any useful advantage.

But what I DO use a lot are various Sonoff products, because they are convenient, practical, affordable... and in most cases, usable as-is.

I have over a dozen Sonoff devices - all already installed with Basic - so unfortunately I am not yet able to confirm the reported existence of a utility which allows 'out-of-the-box' Sonoff firmware to be flashed with new firmware OTA with no UART connection needed... ideal for items like the B1.

Hardware Tips

You'll probably want a breadboard - so be aware that if the thin red and blue lines don't run unbroken full length, it is because they are denoting a track break, so applying power to one side of the breadboard won't power the other side unless the supply rail gaps are bridged with jumpers.

You'll probably get a pack of assorted length male2male jumper cables, but you may also want 30cm male2male, male2female, female2female.

I cut up and join some jumper wires to make a variety of male/female dupont "Y" adapters to allow more than 1 connection to a single pin or skt.

I also do something similar with a couple of 4.7K resistors to make a 3-legged i2c pullup assembly with a common +V connection.

Typical 'tactile' momentary push-buttons have a tendency to pop out of breadboards, so I usually connect to a multi-switch module (not a matrix).

While your soldering iron is hot...LEDs are quicker and more convenient to use if an appropriate current limiting resistor is already attached.

I have some breadboard-friendly 6 LED modules (can't understand why they didn't do 8 LEDs) with integral 1K limiting resistors. But it is worth pointing out that if for instance I wished to display individual switch status leds for all inputs of an 8 port expander it would either require 8 gpio outputs to have one for each of the leds, or require a second 8 port expander configured specifically as outputs for the leds.

A more practical alternative could be to use a single gpio pin to address as many neo-pixels as I could realistically need (potentially hundreds). I will be doing a section on neo-pixels later, but suffice to say now that a neo-pixel is basically a clever RGB LED plus driver chip with a digital input, plus a digital output for optionally feeding into a following neo-pixel. Each neo-pixel takes the 'address' of its position in the chain, and each is capable of being controlled independently by sending an RGB colour code to its address (or all can be addressed at once). Neo-pixels are available as single pixels, or in a hard stick of 8, or rings of 8, 12, 16, 24 etc, or wired into strings, or as flexible 'tapes' of 1m or more, or 8x8 or 16x32 matrix grids etc... and the digital output of any neo-pixel can be chained into the digital input of any other irrespective of their styles. Each and every neo-pixel is individually addressable, and their RGB colour values are all individually controllable between 0 (off) to 255 (full on).So in the case of the example 8 switch port expander, an 8 neo stick could allow displaying the status of all ports in any chosen colours... using 1 gpio.

Breadboard power supplies have USB power inputs, as do all the ESP devices with onboard USB UARTS, and many other modules with USB.

But you'll probably want to reserve your computer USB port for flashing and serial data, so you may want to buy a few cheap USB chargers.

A USB power bank can be a handy device for powering mobile projects on-the-go... some have solar chargers to keep themselves topped up.

Buying Tips

All these sorts of items are available off ebay with free delivery on a slow boat from China for less than it costs to drive to your local supermarket.

If you select "Buy it now" Format then wait for screen refresh, then select "Worldwide" Item Location and wait for refresh, then tick "Free postage" Delivery Option, you will be presented with new items available for sale to other countries at perhaps better exchange rates still with free delivery.

if you enter .99 for example into the Price "to" window then click the ">>" button it will only list any items costing less than a quid.

If a cheap free delivery item is available for about the same price from several sellers, and is cheap enough that I decide to get more than one of them, I have learned not to put all my eggs in the same basket by ordering multiple items from the same seller... if it is free delivery then it doesn't cost me any more to order only 1 from several different sellers, then if there is a problem with any one item, it won't affect any of the others.

Similarly I have learned not to order many items at a time from a seller - it doesn't benefit me if a seller bundles many free delivery items into one bigger package, but it will be worse for me if there is a problem with a bigger package of many items, so I spread them out to be sent individually.

Be aware that there is a growing group of cheating scammers who deliberately undercut prices to grab the custom, but with no intention to supply.

You could be waiting several weeks for delivery, then eventually need re-imbursing by ebay when it becomes evident it was a scam seller.

But you can usually spot such scammers simply by looking at their total transactions... I would rather pay the going rate to a seller with a rating of tens of thousands rather than risk being conned by a deliberate scammer with a rating of less than 2000 because of trying to save a few pennies.

So if you've had good dealings with a seller, go back to him knowing he's genuine, rather than risk penny-pinching to slightly cheaper unknowns.

Occasionally some items don't work, occasionally some don't arrive, but the paypal money back guarantee means you never need to lose out.

Most ebay sellers are very protective of their feedback reputation, so will attempt to keep you satisfied without you needing to complain to ebay.

If you do need to escalate a problem to ebay you have a realistic expectation of receiving satisfaction, which is more than you may get elsewhere.

Ali express does not impose any sort of 'honesty' feedback system on their sellers, and has more financial incentive to favour their sellers rather than the victims, therefore dishonest sellers with no reputation to protect and no fear of reprisal can (and some do) openly lie and cheat to 'rip off' buyers knowing there is nothing their victims can do about it. If you only receive 1 item costing a fiver when you ordered and paid for 4, it becomes a very expensive item - and the seller knew what he intended doing when labeling quantity 4 on a package that was only big enough for.

Wherever you buy from, any ripoff scammer who is deliberately baiting a honey trap can obviously under-cut the best prices of all genuine sellers.

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