#524 Lucky 4D Printer

A “Lucky 4D” number generator, built with a JP-QR701 Thermal Printer, including a detour into to print Chinese (GB2312-80).

Build

Here’s a quick demo..

Notes

So now I’ve figured out the basics of using the JP-QR701 Thermal Printer (see LEAP#523 Basics), time to do something a little more interesting(?)

Singapore has a “4D” (four digit) lottery that is especially popular during festivals like Chinese New Year.

This project generates “Lucky 4D” numbers at the press of a button. It’s a simple build, but I threw in an extra challenge - finding out how to get it to print Chinese characters.

Printing Chinese (GB2312-80)

The JP-QR701 specifications indicate that it has GB2312 support. I think this also applies to similar products that all seem to come from the same OEM or at least from the same design.

Most documentation - especially that found from English-language distributors - is however lacking in any detail on how to use the Chinese language support.

After a bit of digging around, I eventually found some documentation on the OEM 厦门精普电子科技有限公司 Xiamen Jingpu Electronic Technology Co Ltd site that revealed the trick - specifically in the QR701 Module Instruction Manual

It doesn’t use the standard character set / code page instructions, but rather uses two additional commands to enable/disable Chinese language support. When Chinese language support is enabled, 2-byte GB2312-80 characters can be written to the printer.

FS & - Set Chinese Character Mode
FS . - Cancel Chinese Character Mode
where FS is “Field Separator” chr(28)

Note: this is not a universal solution - it appears other printers may use other commands. The Kashino Technology CSN-A2 - that I believe may be the OEM for the AdaFruit Mini Thermal Receipt Printer (product ID 597) - appears to uses an ESC 9 n “select Chinese code format” command.

Encoding Some Chinese

I’m going to add 恭喜发财 to my 4D prediction for that extra dose of prosperity. I need the GB2312-80 coding, which I got the hard way by looking it up in some GB Code Tables:

Character	Pinyin	GB code
恭	Gōng	0xB9A7
喜	xǐ	0xCFB2
发	fā	0xB7A2
财	cái	0xB2C6

Adapting the Printer Library

I’m using the Adafruit Arduino Library for Small Thermal Printers, however this doesn’t directly support the required commands, and unfortunately hides away the necessary support functions inside the library’s private interface.

As a quick work-around, I’ve used a local copy of the Adafruit_Thermal.cpp and Adafruit_Thermal.h files and made a single modification: moved the writeBytes methods to the public interface.

So now I can send some Chinese characters (printed with all current settings applied e.g. size, weight, justification) like this:

printer.writeBytes(28, '&'); // FS &; Set Chinese Character Mode
printer.writeBytes(0xB9, 0xA7); // gong
printer.writeBytes(0xCF, 0xB2); // xi
printer.writeBytes(0xB7, 0xA2); // fa
printer.writeBytes(0xB2, 0xC6); // cai
printer.println();
printer.writeBytes(28, '.'); // FS .; Cancel Chinese Character Mode

Construction

The electronics are straight-forward:

barrel jack for 5V 2A power supply
power switch
mounted the leads for the printer connection
female header strips for mounting an Arduino Nano
a jumper that selects whether to power the Nano from the same supply as the printer or from the USB connector
a couple of bulk caps for the Nano supply to smooth out any power fluctuations caused by the printer
push-button connected to Arduino D2 (configured as INPUT_PULLUP)

Breadboard

Schematic

I’ve mounted it all in an old Raffles Hotel mooncake box for that extra (though conflicting) festive feeling!

wiring_up

All ready to play: