ESP8266: ESP-201 breakout board review

Today finally a new package from China arrived containing an ESP8266-ESP201 bought on aliexpress. I had ordered two pieces and each came in a little plastic bag and stuck in protective foam. The bag also contained a tiny antenna that can be plugged into the connector on the board.

Pin layout to your convenience: when plugged into a breadboard
you cannot read the labels on the lower side of the PCB
Please Note: GPIO15 remains connected even after flashing

Board

I ordered the ESP-201 board because I was looking forward to finally own an ESP8266 module which was compatible with my bread board. Annoyingly the connectors for power supply and serial connection are placed in a way which by default doesn’t fit into a normal breadboard. You can however use pliers to bend the four pins in a 90 degree angle so that you can attach the connectors right to it (see picture):
ESP8266 ESP-201: bend TX, RX, 3.3V and GND
pins to fit the module into a bread board
Another annoying design mistake is that the labels for most of the pins are on the bottom side of the PCB. You can’t read the labels when the module is sitting on the bread board. Because of this I drew up the pin layout above. I hope it will help you…
The bottom side of the ESP201. As
you can see, the pins are nice labeled,
just on the wrong side

Flashing Firmware

It took me a while until I figured out that I also had to connect GPIO15 to ground in order to get the board running. After that flashing worked fine and I could transfer the NodeMCU firmware without further problems to the chip.

Available Pins

It seems that all the usual pins are available. See this table here for mapping from the labels on the bottom of the field to the once often used in forums and other sources: https://github.com/esp8266/esp8266-wiki/wiki/Pin-definition
Especially noteworthy is the availability of the T_OUT pin which is the analog-digital-converter (ADC). I’m not 100% sure what the D0,D1, D2 and D3 pins are for. It might be that the are used for the SDIO mode, where you boot from a SD card.

Antenna

The board appears to have a built-in antenna but also offers a connector to the antenna that came with the package. The following table shows the average signal strength of (anonymized) access points in my neighbourhood after running the wifi.sta.getap command on the lua firmware 100 times. Once with the external antenna and once without:
# of access point listed avg signal strength [dbm]
w/ ext antenna w/o w/ ext antenna w/o
AP-1 100 97 -70 -82
AP-2 93 18 -88 -92
AP-3 2 -92 n/a
AP-4 94 1 -86 -94
AP-5 4 -93 n/a
AP-6 16 -89 n/a
AP-7 99 97 -80 -84
AP-8 19 -91 n/a
AP-9 5 -92 n/a
AP-10 100 100 -31 -32
AP-11 100 100 -31 -32
AP-12 98 87 -89 -91
AP-13 40 -92 n/a
AP-14 4 -91 n/a
AP-15 1 -91 n/a
AP-16 16 -93 n/a
AP-17 13 -93 n/a
AP-18 81 92 -89 -92
AP-19 22 -90 n/a
AP-20 47 38 -91 -92
AP-21 99 75 -78 -89
AP-22 95 87 -81 -89
AP-23 6 -90 n/a
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As you can see, 12 access points were not even visible without the external antenna. All others had significantly worse signal strength without antenna. I realize that this test is not highly scientific but it might give you an idea how valuable the external antenna is.

Chip

My two boards are equipped both with the newer ESP8266EX chip. If anybody knows what the difference is to the version without “EX” please let me know. Nodemcu’s node.info() returns these values: 
flashisize flashmode flashspeed
512 40000000

Quality

The board looks well processed but one of the two pieces came with pins not 100% perpendicular to the PCB. However, this doesn’t affect usage since both rows of pins are equally skewed.

Summary

If you don’t mind adapting some of the pins with pliers you get a great test board for a really good price (I paid $4.69, by now it’s even cheaper). Once adapted the module fits nicely into a bread board and you have one row of connectors left on each side of the board. It is a pity that the pins are only labeled on the bottom side but that might be changed in the future. However, for a price only slightly higher than a ESP-01 it is a pretty good module and has many pins more broken out as well. Especially the ADC offers new possibilities for experimentation. Just remember that the ADC measures values between 0 and 1V. The external antenna and the connector on the board is another aspect on the plus side. It is quite impressive how much more sensitivity this 15cm wire yields.

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