I'm making a little scanning beacon gizmo. When a laser shines on it from ~40m away, it is supposed to transmit its ID and HIGH (1) to the laser controller ~40m away. Otherwise, transmit 0 or nothing. There will be another beacon doing the exact same thing, just with a different ID.

These beacons will be battery powered, so I want them to draw as little energy as possible.

Also, I don't know anything about antenna design, so I'll have to use a SiP (System-in-Package) with an integrated antenna.

The best solution I've found so far: the CC2651R3SIPA by Texas Instruments, which has a programmable radio than can do BLE, ZigBee, 2-(G)FSK, and a few other wireless protocols. 125kbps BLE has huge range, I've heard, and this module claims a -104dBm sensitivity for this protocol, which is crazy. The radio does 7.1mA TX at 0 dBm, 9.6mA TX at +5 dBm, and 6.8 mA RX. The MCU itself draws 3.60mA in active mode. I'd experiment if I can use 0dBm, but 5dBm would be fine. This puppy costs $3.49 at scale, which I consider to be quite good.

Laser controller would be using the same chip. GPIOs for this project are all low-spec; don't worry about them.

I'm looking for feedback. Should I instead be using LoRa, for example? I know that operates at license-free 169 MHz, 433 MHz, 868 MHz (Europe) and 915 MHz (North America). My intuition tells me this will be more energy efficient, but idk about the other stuff, like chips that do LoRa.

I'd also like to know what kind of programming experience I'm signing up for. I've had a go at STM32 bare metal in STM32CubeIDE for some LED stuff just to see under the hood and then completed some basic tasks using the HAL (hardware abstraction layer) and CubeMX. What's the TI firmware experience like? What's it like to work with something as advanced as LoRa or BLE?

I've been figuring out various electronics solo over the past year at a startup. I've embarked on my first independent commercial project outside of work: this. Entering the world of modern RF-capable MCU's. I'm afraid I'll have no better way of learning than to just throw myself in this water, however deep, and try to swim out.

A big thank you in advance to any helpful RF chip wizards out there.

Edit: I've come across the CC1110/CC1111. Cheaper and less overkill. Sub-1GHz. Too much power draw, though. That's led me to find the CC1310, EFR32 Series 1, and the SX126x. I'll be continuing down the sub-1GHz path, I think. Thoughts?


1 Answer 1


For distance in the 40 meter range, the 2.4GHz band might work, but 915MHz will give you much more reliable operation. Zigbee on the 2.4GHz might be a viable solution since it is low power ang high efficiency. (greater frequency often makes them more energy efficient). What makes me doubt that it is the best solution for you is your lack of knowledge in RF design. It might be hard to fine tune all the parameters to maximize your performance. On the other hand, LoRa is very straight forward. There are also Xbee s module that are very simple to integrate.

I don't have any experience with the particular chip you listed, but I know some of them can be very hard to setup properly.

My best advice, before selecting a techno and designing a board, buy yourself a few dev board and check their performance. You'll see the choice then is pretty easy to take!

Regarding the regulatory path, I wouldn't consider it. Select the techno that works in your first location, then add some. The norms are very different and finding a tech that will suit both will be more complex. You are often better to design two version one for europe and one for america.


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