Arduino Library for SX8646 Capacitive Button Controller

The router front panel with LCD I began interfacing has a capacitive five button keypad. The panel I'm talking about was used by Sercomm SHG1500 routers and although there are multiple hardware versions of the LCD (some make use of FPGA circuits to drive the LCD, others use SPI interface), the keypad seems to be the same. Based on Semtech SX8646, it is controlled over I²C bus.

SX8646 requires 3.3 V power and is not compatible with 5 V bus. Besides I²C, it uses another pin to trigger an interrupt at host when a button is touched. The keypad PCB sits next to LCD PCB and on some hardware versions it plugs straight into it, while on others it uses a connection cable going to the router main board.

SX8646 keypad PCB

Arduino Library for HX8347-I Router Front Panel LCD

A while ago I managed to wire the front panel of a Sercomm router to a STM32 blue pill development board and I have attempted to control the color 2.8" LCD and the capacitive keypad found on the front panel of this type of router. Long story short: if you own a discarded Sercomm SHG1500 router that reports LCDv6 "gateway hardware version", this is the front panel you can control. OpenWrt can't be currently installed on these routers and there is no known way of changing their firmware or having access to bootloader.

But the front panel can be a great module if you're into electronics. It has a 2.8 inch LCD and a 5 keys capacitive keypad next to it. Hardware version LCDv6 uses a HX8347-I based LCD with SPI write only interface. The keypad uses I²C bus and an additional pin to trigger an interrupt when a key is touched. More on that in another post. Interfacing the front panel to common 2.54 mm pinheaders is not straightforward since it uses a 2x15 pinheader with 1.27 mm pitch. But I built an adapter you can find in the other post.

Truly HX8347-I LCD showing the SMPTE pattern

HTTPS Server on the ESP8266 NodeMCU

NodeMcu is a development board based on ESP8266. This microcontroller is made for IoT applications and features WiFi connectivity. There is an easy way to program ESP8266 boards using Arduino IDE. This is what I will use here too. Nowadays, internet security is very important. Maybe you'll use ESP8266 only in the local network or you'll allow external access to it. Unless it's behind a proxy, leaving it unsecured is not a good idea. In the last years, most of the websites switched to HTTPS and modern browsers display warnings when requesting an unsecured HTTP page.

To offer secured content, a server greets the client with a trusted certificate, issued by a known authority. The certificate has a limited time validity and must be renewed from time to time. In this post, we'll generate a SSL certificate and use it on ESP8266 web server. You can buy the certificate from a known authority or you can generate it for free on your computer. I'll use the second method although is comes with a glitch. The browser will not trust the certificate. But that's OK, you can trust it as long as you generated it and you keep it private.