By Xie Bo | December 22, 2024
Radiolink launched the AT10 in 2013 and the AT9 in 2014. After multiple iterations, both models remain popular to this day. The AT9 has even been the first remote controller for numerous hobbyists and college students, with its market price staying above 500 RMB.
Later, as we expanded into youth education programs, teachers from primary and secondary schools kept suggesting we develop a remote controller priced around 300 RMB. While our T8FB and T8S fit the budget, they feature no built-in display and require a phone or computer for parameter setup. For years, I carefully evaluated this price range, yet found it impossible to maintain the user experience we stand for. At Radiolink, we never compromise product quality for lower prices, so the project was put on hold.
After successfully developing the RC8X, our team gained in-depth expertise in FreeRTOS and LVGL. Meanwhile, domestic microcontrollers became more powerful and affordable. Our partners also encouraged us to launch a mainstream, cost-competitive model to expand our market reach.
In recent years, we have released only a few new remote controllers. Our core principle is simple: every new product, regardless of price point, must deliver solid performance, appealing appearance and premium overall feel. For two weeks, I took our existing controllers home after work. Standing on the terrace at night and gazing into the distance, I brainstormed ways to make breakthroughs in material selection, BOM design and manufacturing, striving to strike the perfect balance between performance, functionality, ergonomics and cost. With the target price finalized, our goal was to build an exceptional product within the budget.
We started with circuit optimization. Following the design of the T8FB, we adopted a single integrated circuit board that accommodates all controls including knobs and switches, effectively cutting manufacturing costs. We selected a cost-effective domestic main control chip priced at just 5 RMB, which meant superior software design was essential to guarantee great user experience. We paired it with a mature 2.8-inch LCD panel for mass production, balancing display size, refresh rate and cost efficiently.
Next came the exterior design, developed by the same design team behind the AT9 and RC8X. The look may not be radically innovative, but it is timeless and stylish. We also partnered with the same mold factory. Retaining our classic design language while elevating the overall quality was achievable. The real challenge was working within a tighter budget to upgrade texture, grip and value — a true test of our team’s capabilities.
The T12D features a white casing, which is far more prone to surface defects and leads to a higher reject rate. Still, we refused to compromise on aesthetics. We worked with our manufacturing partner to improve production techniques, aiming for a higher yield rate for white units than black ones to offset extra costs. Every stage presented new challenges, and overcoming them would lay a solid foundation for our future products.
With the appearance finalized, we focused on ergonomics, especially gimbal performance. The gimbal used in the AT9 had served us well for a decade, but its production cost was high. I fully disassembled and reassembled the gimbal for the first time to explore improvements. After analyzing factors affecting operation feel, I discussed ideas with our structural engineers the next day. We decided to replace ball bearings with brass bushings to reduce costs, without sacrificing smooth control. Brass bushings are adopted by brands like FUTABA, whose gimbal feel even outperforms our previous ball bearing design, proving there was room for improvement.
After days of discussion and trial mold revisions, we found that the brass bushing design delivered an even better feel than the original high-cost ball bearing structure. Targeting our main user group who rarely adjust gimbal height, we set the gimbal at an optimal fixed position. Compared with CNC machining, die-casting for fixed-height gimbals drastically lowered costs while suiting most users perfectly. Through thoughtful design optimization, we managed to reduce costs while maintaining and even enhancing user experience.
The final and most challenging part was software development. A new product deserves new features. Unlike the basic firmware of the AT9S, the T12D runs on FreeRTOS with a brand-new GUI to fully leverage the color display. It offers full compatibility with external RF modules and adds voice prompts — features commonly seen on remote controllers priced over 1000 RMB. What’s more, the voice prompts support user customization, instead of fixed factory settings. We also streamlined the menu system, so users can operate it intuitively without reading a manual. In short, we aimed to pack comprehensive, premium features into an affordable model.
We pushed forward every day with excitement and uncertainties. After simulating all interfaces on computers, we ran the software on the physical controller, only to face a major issue: the screen refresh rate was extremely slow. It took nearly 3 seconds to refresh, with content scrolling visibly line by line. Our theoretical calculations ruled out issues with GUI rendering or data transmission, and we finally traced the problem to driver errors.
Once the refresh issue was fixed, full-load operation still lagged, caused by excessive semaphores generated during multi-task processing. Fortunately, FreeRTOS is open-source. We revised the underlying scheduling code, changing event-triggered message transmission to regular timed transmission, which greatly reduced data traffic. Eventually, the GUI and menu navigation of the T12D became smoother than those of many high-end 1000+ RMB controllers with dedicated GUI hardware circuits.
Beyond controller upgrades, the bundled 12-channel receiver R12F is equipped with a Type-C port for user firmware updates, making it Radiolink’s first upgradable receiver. In addition to traditional PWM, PPM and SBUS outputs, it adds a CSRF interface. Our legacy T-series controllers supported a maximum of 8 channels, while the updated FHSS_V2 protocol expands channel count to 16. All channels adopt 12-bit full-range output with a precision of 0.25μs, outperforming all previous Radiolink products and most mainstream controllers on the market. The R12F remains fully compatible with all older T-series transmitters and surface controllers. The T12D also supports V1 protocol to work with legacy receivers. At Radiolink, we always prioritize backward compatibility to save users from extra trouble, no matter how much extra work it brings to our R&D team.
Due to market positioning strategies, we reserved full voice prompts and advanced script parameter settings for external RF modules exclusively for our 16-channel T16D model. Even so, the T12D works seamlessly with most third-party open-source external RF modules, with no compatibility issues after module firmware updates.
The T12D + R12F combo is priced at 359 RMB. It delivers intuitive, fluid operation, user-friendly menus and exquisite UI, along with premium texture comparable to high-end products. Its performance once again pushed our limits.
The founder of technology education at Shenzhen Mingde School was attracted by the T12D images on our official website, yet doubted its quality given the low price. He kindly warned me that impressive product pictures might lead to disappointment and harm our brand reputation. I assured him the real product looked even more sophisticated. Skeptical at first, he fully agreed after receiving the unit the next day.
The T12D was an instant hit after launch. More than sales figures, I value user experience the most. This cost-effective product with multiple innovative features was built with zero compromises. I rejected numerous prototypes during development, leaving engineers unsure about my standards. They often asked for my approval after each revision, and many feared the project would be canceled. I always said Radiolink has no shortage of products, but we will never launch anything with subpar experience. We live up to user expectations and safeguard our brand reputation.
I’m grateful to all R&D team members. They stayed calm even when I was emotional, shared my pursuit of perfection, and paid close attention to user feedback. Nothing is more rewarding for engineers than praise from satisfied users.