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Review by Tim Blythman BrisbaneSilicon ELM11 Microcontroller Board The inexpensive ELM11 development board from BrisbaneSilicon uses the Lua programming and scripting language and is fairly inexpensive. It’s great to see this type of thing being designed in Australia, so we were curious to try it out. T he folks from BrisbaneSilicon (https://brisbanesilicon.com.au) work in FPGA (field programmable gate array) and embedded systems engineering. They contacted us to see if we were interested in trying out their ELM11 microcontroller board. ELM stands for Embedded Lua Machine and, as you might expect, it can be programmed using the Lua language. BrisbaneSilicon sent us a couple of ELM11 boards to experiment with; here is what we found. Lua Lua is an interpreted scripting language that was originally developed to streamline data entry at a Brazilian petrochemical company. It has developed into a simple yet powerful language that is used in many places where a scripting language is needed. That includes games and embedded (microcontroller) environments. Scripting languages are generally easier to use and develop for, especially for particular applications, with the trade-off being that they are usually slower and more memory intensive than compiled languages like C or C++. Lua is the Portuguese word for moon; one of Lua’s predecessors was named SOL, or sun. Lua’s interpreter is written in the C programming language, so is easy to port to platforms that have a C compiler. It is also designed to easily interface with C code, so it can be used to add scripting to projects written in C. You can read more at https://lua.org/about.html We’ve written a separate panel about the Lua language for those who want to know more. The ELM11 presents a REPL interface, where REPL stands for The ELM11 is a compact and tidy development board that provides an embedded interpreter for the Lua programming language. There isn’t much on the underside of the board apart from pin markings. All the components are on the top of the board, including two tactile pushbuttons and numerous LEDs. The ELM11 includes a Gowin GW1NR FPGA and a separate microcontroller that provides a virtual USB-serial port and can also reprogram the FPGA chip. 90 Silicon Chip Australia's electronics magazine read, evaluate, print and loop. You can also write and then run complete programs for more complex tasks. In this regard, it is similar to devices like the PicoMite running MMBasic. MicroPython is similar; it can run on many microcontroller boards, including the Raspberry Pi Pico. All these devices and languages allow you to enter simple commands or write and run complex programs. The ELM11 The ELM11 measures 60 × 26mm and has two rows of 18 pins on a 0.1inch (2.54mm) pitch with 0.9 inches (22.86mm) between the rows. This is a fairly standard layout for modern development boards, allowing them to be easily used with breadboards or prototyping PCBs. The pin headers are provided loose and need to be soldered to the module. The ELM11 is shown in the photos. It has a USB-C socket, which is good, since they are much more robust than the micro-B USB sockets that are sometimes seen on boards like this. Interestingly, the large chip that you might expect to be the microcontroller is in fact a Gowin Semiconductor GW1NR FPGA. An FPGA is made of many logic elements that can have the connections between them rerouted after production. It can be compared to how you might program a microcontroller to customise its operation. Microcontrollers are also made of logic elements, so an FPGA can be programmed to behave as a microcontroller, among many other things. The GW1NR comes in a QFN-88 siliconchip.com.au package (quad-flat no-leads with 88 pins) and incorporates 8640 LUTs (lookup tables) with 8MiB (64Mib) of RAM. It also has a smaller amount of BRAM (block RAM) and includes flash memory to store the configuration bit stream. There is a separate Puya P25Q32SH 4MiB (32Mib) flash memory chip in a SOIC-8 package, which is available as non-volatile storage for the Lua interpreter. The smallest QFN chip is a TMI7003 three-channel power management IC that incorporates a buck regulator controller. It provides the multiple supply rails needed by the FPGA chip. The remaining QFN chip is a BL702 RISC-V microcontroller that is used to provide a USB interface to implement a virtual serial port interface for communicating with the Lua interpreter. It also provides a JTAG programmer that can be used to reprogram the FPGA. There are 36 pins available on the two headers, four of which are for power: 3.3V, 5V and two ground pins. The remaining pins are numbered from one to 32. Sixteen (1-16) of these pins are for general purpose I/O, while the remainder are labelled as an I/O bus. The I/O pins operate at 3.3V levels. Fig.1 shows the pin mapping of the ELM11, including the peripherals that can be mapped to each pin. The mapping is set by the FPGA configuration, and it appears that different ‘hardware overlays’ are possible. This can change which peripherals are available on which pins, amongst other features. There are also several LEDs on the board with different functions. Three are configured to reflect the status of I/O pins 1, 2 and 3, making it straightforward to start blinking the LEDs with Lua, without connecting any external hardware. There are two small tactile switches. One can be used to reset the ELM11, while the other can be detected on I/O pin 1. This combination of a GW1NR FPGA and a BL702 microcontroller can also be found on the Tang Nano 9K development board. More information on the Nano 9K can be found at siliconchip.au/link/ac9z Using the ELM11 The ELM11 presents a virtual serial port to communicate with the Lua REPL interface. It operates at 115,200 baud, 8 bits, no parity and one stop bit. Screen 1 shows the prompt after booting, plus a few commands and their responses. We used the Tera Term terminal program under Windows. We found it easy to enter Lua statements at the terminal prompt; the results are printed back to the terminal. The import statement is needed to load the functions used to access features like the GPIO pins. A simple import(“all”) can be used to quickly load all extra functions, although you can also import individual functions to reduce memory usage. BrisbaneSilicon has provided some simple code examples that can be used in the REPL. They are set up to be copied and pasted directly into a terminal program and can be found at https://brisbanesilicon.scrollhelp.site/ emblua/example-usage We found that we had to set a 100ms per line delay in TeraTerm to allow the processor to complete the import command for multi-line examples; this appeared to be more than sufficient for other commands. This setting can be found in TeraTerm’s menu under Setup → Serial port… → Transmit SPI UART PWM Function Pin Pin Function TX TX PWM GPIO 1 19 I/O BUS CS, CLK, TX RX PWM GPIO 2 20 I/O BUS CS, CLK, TX TX PWM GPIO 3 21 I/O BUS CS, CLK, TX RX PWM GPIO 4 22 I/O BUS CS, CLK TX PWM GPIO 5 23 I/O BUS CS, CLK RX PWM GPIO 6 24 I/O BUS CS, CLK, RX TX PWM GPIO 7 25 I/O BUS CS, CLK, RX RX PWM GPIO 8 26 I/O BUS CS, CLK, RX TX PWM GPIO 9 27 I/O BUS CS, CLK, RX RX PWM GPIO 10 28 I/O BUS CS, CLK TX PWM GPIO 11 29 I/O BUS CS, CLK RX PWM GPIO 12 30 I/O BUS TX PWM GPIO 13 31 I/O BUS RX PWM GPIO 14 32 I/O BUS TX PWM GPIO 15 33 I/O BUS RX PWM GPIO 16 34 I/O BUS GND 17 Fig.1: The data sheet includes this I/O pin 5V 18 map that also shows the layout of the main features of the board. The button at upper left is RST and the other one to its right is BTN1. Note that the pin numbering shown here is different to that printed on the PCB silkscreen. 35 GND 36 3.3V siliconchip.com.au May 2026  91 Australia's electronics magazine delay. The GPIO and PWM examples are designed to use the onboard LEDs. Even without having much knowledge of the Lua language, it was simple to copy and paste example code from the BrisbaneSilicon website and see the results on the LEDs and console immediately. The library functions are detailed at https://brisbanesilicon. scrollhelp.site/emblua/api There is also a so-called Command Mode, which is used to access system and configuration settings. You can also use it to do things like upload programs. A Python program is required on the host computer to upload the program over the serial port. Programs can also be run from Command Mode. We tested the program upload utility and found it worked well enough, although it is necessary to disconnect the terminal program to allow it to access the serial port. Complete programs can be found at: https://brisbanesilicon.scrollhelp.site/ emblua/example-programs The reset button can be easily used to reset the processor to get back to a known state. A running command or program can be interrupted by pressing the ‘q’ key. The ELM11 data sheet has more detail on the interface; see https:// brisbanesilicon.com.au/docs/ELM11_ Datasheet.pdf ESR Test Tweezers Complete Kit SC6952: $50 June 2024 siliconchip.au/Article/16289 This kit includes everything needed to build the ESR Test Tweezers. The three resistors and single capacitor needed for calibration are also included. But this kit does not include the CR2032 (or CR2025) coin cell or optional 5-pin header CON1. The board we received is a beta (pre-production) release of the ELM11, and the data sheet notes that some of the SPI and I2C functions are not implemented yet. We were able to bit-bang I2C data using GPIO pins to (slowly) drive a small OLED module. Other I/O features such as PWM (pulse-width modulation) and UART (asynchronous serial) worked as expected. There is also a help statement that prints out a user guide on the serial terminal. The ELM11 platform The ELM11’s architecture has been optimised for working with Lua. BrisbaneSilicon refers to this as ‘hardware acceleration’. The advantage of using an FPGA is that the processor core can be tweaked to improve performance for the intended use; in this case, as a Lua interpreter. The ELM11 data sheet notes that different so-called hardware overlays are available. These appear to include options like different I/O features and processor characteristics. It also appears that it may be possible to configure it with a multi-core processor. Using an FPGA also enables the ability to add other so-called IP cores. These are modular features that can be added to the FPGA fabric and could include things like display and communication drivers or other processors. Some examples are listed at https://brisbanesilicon.com. au/ipcores With its similarity to the Tang Nano 9K, it may also be possible to use the ELM11 as a general-purpose FPGA development board, although we have not investigated this in detail. Conclusion Screen 1: the interactive Lua prompt can be used to enter commands and see responses. The last three commands are all that are needed to light one of the LEDs on the board. 92 Silicon Chip Australia's electronics magazine The ELM11 combines several interesting features. Lua is simple yet powerful, making the Embedded Lua Machine easy to use and versatile. The FPGA platform offers a lot of flexibility in that it can be configured with different capabilities using hardware overlays. Even though we rarely use the Lua language, we found the ELM11 easy to use, with many examples that can be run on just the bare board or with some components on a breadboard. It’s an inexpensive way to learn Lua in general and to provide an embedded environment. The ELM11 is available online from BrisbaneSilicon for US$14.95 (about AU$21) before shipping – see https:// SC brisbanesilicon.com.au/elm11 siliconchip.com.au The Lua Language This is not the first time we have encountered Lua; the Mini Wireless Webserver (using the OpenWRT firmware) in the November & December 2012 issues (siliconchip. au/Series/20) was configured and programmed using Lua. Its utility as a scripting language is well-established, and the open-source OpenWRT router firmware uses Lua extensively. OpenWRT’s web configuration interface is called LuCI (Lua Control Interface) and, as we saw from the Mini Wireless Webserver, Lua can even be used to generate custom web pages. Lua has been used for scripting and automation in computer games since at least 1997, when it was used by LucasArts in the framework of their Grim Fandango adventure game. It is estimated that about half of all Lua users are involved with game development. The NodeMCU project for Espressif microcontrollers (such as the ESP8266 and ESP32) allows boards based on these chips to be programmed using the Lua language. See https://github.com/nodemcu/ nodemcu-firmware In these applications, Lua is used similarly to the likes of Micromite BASIC, PicoMite MMBasic or even MicroPython. If you have seen some Lua code, you might think it doesn’t look very different from these languages. It does have subtle differences, but it is fairly forgiving and easy to learn. Some background is provided at www.lua.org/ history.html The designers have aimed for simplicity of the language, so it is not surprising that it looks like other languages. The webpage above indicates that the optional use of semicolons (as statement separators) in Lua came about to appease users of both C and FORTRAN! A minimal Hello world program looks like this: print(“Hello World”) Lua implements well-understood control structures like if/then/else/ end and while and for loops. The for loop uses the keywords for, do and end; each control structure has a siliconchip.com.au corresponding end statement, so the scope is clear. Interestingly, variables do not have a type, but values do. The types include number, string, function and table. There is also a nil type, which is understood to be the default value of an uninitialised variable. Functions can be defined and can return one or more values; a function can even be assigned to a variable. Lua supports multiple variable assignments in the same statement. Tables are associative arrays; this means that the index does not have to be a number. Tables can be used to implement ordinary arrays, sets, lists, dictionaries, trees and queues. There is a variant of the for loop that can be used to iterate over the items in a table. One thing to watch is that numeric array indexes are 1-based, unlike many other languages (eg C/ C++ are 0-based). So-called meta-tables can be used to override the behaviour of mathematical operators when non-­ numeric arguments are provided. Thus, they can be used to emulate object-­oriented methods. The developers of Lua call these features meta-­ mechanisms. The intent is to keep the underlying language quite simple, but provide a means for a programmer to create complex behaviours when required. These advanced language features might sound intimidating, but if you are looking to use Lua for straightforward scripting, you don’t need to use them. If you are comfortable with the likes of MMBasic, you’ll probably need to do little more than learn a few different keywords and some minor syntax differences. If you have worked with BASIC, C or Python, aspects of Lua like expressions and mathematical operators will appear familiar. Numerical values are typically stored as floating point, but some implementations (including the ELM11) use 32-bit signed integers. It’s worth remembering that Lua code is case-sensitive. Like Python, the language can be extended with the import keyword. For example, the interface for the I/O features of the ELM11 is simply a set of functions that can be imported to make them available to the interpreter. Lua’s simplicity also means that is also renowned amongst interpreted languages for its speed. Summary Lua is an interesting language, and we found it easy to learn the basics. Despite this, it can be extended in multiple ways to provide advanced programming features. Here is a relatively simple sample program: #!/usr/bin/lua print(“Content-type: text/html\n”) print(“<HTML><HEAD><TITLE>Relay control</TITLE>“) print(“</HEAD><BODY>“) local f = io.open(“/dev/ttyACM0”, “r+”) f:write(“quiet\n”) if os.getenv(“QUERY_STRING”):upper() == “ON” then f:write(“D0=1\n”) print(“Relay is now on.”) elseif os.getenv(“QUERY_STRING”):upper() == “OFF” then f:write(“D0=0\n”) print(“Relay is now off.”) else print(“Error.”) end f:close() print(“</BODY></HTML>\n”) This snippet of Lua code was presented in the series on a Mini Wireless Webserver to generate a web page and send data over a serial port to control a relay. Even if you haven’t used Lua before, it’s fairly clear how the program works. Australia's electronics magazine May 2026  93