If you are a regular reader, then the odds are you have taken apart an electronic gadget, either for a fix, or simply because your curiosity got the better of you. Once inside, it’s all but impossible to help yourself from doing at least a little reverse engineering. That’s what happened when [PRBS23] took a look inside a MasterBuilt Gravity 800 Grill for a simple wire fix. But one thing led to the next, and now open source firmware for the grill is freely available!

The first order of business in creating the firmware is reverse engineering the original controller. Opening it up immediately reveals an ESP-32 and a well-labeled programming port. The rest of the control board is equally simple, including connectors for four thermistor temperature sensors, lid open/close switch, fan driver, 16 segment LCD, piezo buzzer, and some physical inputs.

The thermistor along with the physical inputs are connected to a 16 pin chip, interfacing with the MCU over a 9600 baud UART connection. [PRBS23] cannot determine an ADC chip meeting these specifications, so the most likely answer is a cheap MCU programmed to act as a simple analog fronted.

The neatly labeled programming header is used to quite easily dump the firmware with the espflash utility. Analyzing this dump reveals a rather strange ADC correction function used by the original firmware. The necessity and overall utility of this function remains unclear, does corrects a maximum of around 40 degrees Fahrenheit.

Most of the other features ended up being at least somewhat easier. The CS1621 segmented display driver is reasonably well documented with datasheets making its implementation far easier. Likewise, the other odds and ends were implemented in a far more normal manner compared to the thermistors.

All this reverse engineering work got tied together into a neat little firmware package. It comes with over the air updates PID controlled temperature, and a real-time web interface. This also isn’t the first time we have seen an IoT device liberated from proprietary firmware, and this remains one of our favorite uses of reverse engineering!

In the 1960s, the home computer was barely a twinkle in anyone’s eye. This was the decade in which computers were used by a handful of companies and organizations and took up entire rooms. It was the decade that saw the birth of the first integrated-circuit computer, the Apollo Guidance Computer, and, rather strangely, one of the first home computers of sorts: the Digi-Comp 1.

In 1963, E.S.R. introduced this little programmable educational toy computer. It relies on simple mechanical logic gates, programmed by positioning tubes on sliders. Their original intention was to create actual computers, but one thing led to the next, and E.S.R. became the premier educational computer toy company of the 1960s. The Digi-comp is a rather simple device. A program is entered by soda-straw-like tubes placed on sliding rails. These tubes interact with spring-loaded levers which move in accordance with the “clock” switch. The result is a simple binary computer you can program.

[Chris Staecker] got a remarkably well-preserved Digi-Comp I to demonstrate its unique functioning. With some rubber bands and a touch of modern technology in the form of 3D printing, [Staecker] got the toy working like new. The programming process is quite manual, and its functioning is not obvious. But it can compute binary outputs of given functions. Unfortunately, this is not a Turing-complete process, but rather a state machine with 8⁸ (or 16,777,216) possible states. The toy, with all its limitations, is highly reflective of the state of computing at the time, and a rather neat look at what the future was, back in 1963.

Make sure to take a look at E.S.R.’s successor to the Digi-Comp I, the creatively named and quite different Digi-Comp II. We’ve looked at other old “sort of” computers like the Geniac. You can even simulate that one in your browser.