wova21

Hi all,

I found out about this thread about a week ago and absolutely loved it. I took everyones efforts and put it in a new design to what I think (from my background) will work best.

I followed Howard's approach on creating a 5MHz carrier because in my opinion it's not worth the effort to put this burden on an MCU for a simple binary modulation as this one. The way how Howard designed the spiral loop antenna for this application also receives my preference in terms of output strength (when tuned properly).

On our track we only drive 2S up to 6S powered cars so I opted for a power management solution that allows receiving power from any of these battery packs. It is very much possible to design a tiny power management circuit for a 1S pack as well but in my approach where I have very limited board space I had to make a choice because increasing the input voltage range from 1S to 6S requires more board space. You can actually keep my current design and simply swap U3 with an ultra low dropout voltage regulator that has the same pinout and SOT-23 package.

I like the idea how firmware in ESC's can be configured/upgraded through a 1-wire interface. I was thinking about doing something similar by first flashing the MCU with a bootloader that accepts new firmware to be uploaded using 1-wire protocol. This way you don't need to have physical access to the PCBA for reflashing the MCU but is everything reprogrammable through the 3-wire cable that is brought out. Therefore I went with an ATMEL because I have most experience with this manufacturer for applications such as this one.

I shrunk everything down to a 20x20mm SMT only PCBA. This is still hand solderable but I admit that it is quite a challenge.

I'll build a couple units early August. Send me a PM if you want to join in with the programming. After tuning the first units I'll send one out to those that believe they can be of any help (You will need an AVR ISP capable flasher to flash the MCU directly and an Arduino nano for example if you also want to test/use the 1-wire upload ). I'm sending out 5-8 units.

I use a handy tool to flash the MCU directly through the ISP interface because then I don't have to bring out any additional programming pads or a connector. There is simply no room for it anyways. Since I'm new here and this is my first post I am not allowed yet to post URL's so if you google "ATmega firmware flashing tool" you can see what I am talking about.

Attached are the PCB layers. I'll post a 3D render and schematics in the next post.

Any comments/concerns/remarks are welcome.