Your magnetometer/compass is not working with INAV? Is the sensor red in Configurator? You are not the only one… Not only most popular compass HMC5883l is discontinued and what you get are Chinese clones, chip labeled 5883 might not be HMC5883l but something completely different. And I2C bus is very very picky and likes to give up on you….
This is how you might fix your problems: add pullup resistors for I2C SCL and SDA lines and/or lower i2c_speed…
One of the things I like about Arduino ecosystem is that you can prototype pretty decent device in very short time. It might not be pretty, but will work. Just like my DIY hygrometer built with DHT11 and SS1306 OLED display I've built few weeks ago:
Simple, efficient and runs on 4 AA batteries. The best part is that it can be powered all the time. Arduino does humidity measurement, display the result and then powers itself down to conserve power. Cool, right?
Code is available in GitHub repository.
Weather outside is bitchy. Period. It rains, then it's windy and then maybe there is some direct sunlight for 15 minutes. No way to fly or test my DIY RC radio link.
But, there is some progress after all. My latest changes seems to be working just fine. On a bench link was stable for almost 3 hours. Later I too it for a standard range test: 2.8km LOS. It also worked, I still had around 5dB of link budget left on a ground level.
Back to the topic. Crossbow LRS is open source and open hardware. Maybe open hardware is too much, since there is almost no hardware to build. After all, first iteration is based on LoRa32u4 II development boards and running good old Arduino.
RX module requires no additional hardware:
TX module is slightly more complex. It required voltage stabilizer and inverter/level shifter made with single 2N7000 FET transistor. I2C OLED display is an option:
Idea for Crossbow, DIY LRS system did not appearned in my mind out of nowhere. All my previous LoRa attempts were aimed at telemetry purposes only. E45-TTL-100 are cool, but bulky. If I would want to use them, I would either have to attach Arduino to it or hack it open and reprogram onboard CPU (like Qczek LRS does). Somehow it was not something what suited me very much.
But then I came across Adafruit Feather LoRa32u4 RFM95. Awesome idea. ATmega32u4 and HopeRF RFM95 LoRa module on one PCB, Arduino compatible, reasonably small and light. As a bonus, can be LiPo battery operated and has own 1S LiPo chanrger. The only thing I did not liked (OK, not the only one, but that was the biggest one) was price tag: $34.95 is somehow slightly more than I'm willing to pay for ATmega32u4. Even with radio module. So, after some digging on eBay I've found something that looked like a clone of Adafruit Feather LoRa32u4 RFM95: BSFrance LoRa32u4 II.
After determining that range of 868MHz LoRa wireless modules E45-TTL-100 have, at least, quite impressive range (5,7km and I was out of line-of-sight to test further) I’ve decided to test something else.
In the beginning I was planning to use those radio modules for telemetry only, but then another thought crossed my mind: why not to build DIY TBS Crossfire for the poor? After all, TBS Crossfire also uses 868MHz LoRa (SX1272 vs SX1276), so it should be possible to build DIY radio link for medium range (up to 5km) for RC planes, right?
First of all, I will need to know how fast data can be transferred and how much delay can I expect in real life. So I’ve modified Arduino code and E45-TTL-100 configuration:
Results:
Few facts about SEMTECH SX1276 LoRa modem and 20dBm (100mW) mode:
The biggest problem with +20dBm on PA_BOOST is allowed 1% duty cycle. On the other hand, +17dBm mode (50mW) does not have such a limitation and maximum range should be only 1.42 times shorter than in 100mW mode.
I have a nasty habit of buying things and then forgetting about them. Something like that happened to Tiny Frsky 8CH Receiver (Wolfbox F802 software compatible) from Banggood I’ve purchased last year. For some time I used it in JJPro P175 quadcopter, but then it landed in a box and I forgot about until last week.
So, let’s do overdue “hands on” on Tiny Frsky 8CH Receiver from Banggood… (more…)
It was a good weekend. At least for me and CDEbyte E45-TTL-100 868MHz LoRa serial wireless modules based on SX1276. Why? Since weather was nice and looks like those modules are way better than datasheet specifies. Specs states: 3km in open space. And I’ve proven almost twice that much range! Last Friday I’ve placed one E45-TTL-100 with stock antenna on my balcony, took second with me and went for a car ride.
Area around my home is full of small hills and copses, so most of the time something was blocking the line between transmitter and receiver. But every time I was high enough, I was getting clear signal without any packets lost. At the furthest point of my trip I was 5.7km from the transmitter, inside a car and a copse was between me and TX module. That means no line-of-sight and as a result I’m pretty, pretty sure E45-TTL-100 should be able to work on much higher range that that. I only have to find a good place to test it.
With a (more less) free evening I decided to finally start testing range of 868MHz LoRa E45-TTL-100 radio modules I described only yesterday. Instead of building new testing rig, I only upgraded testing setup I used to test range of FS1000A and XY-MK-5V 433MHz radio modules. Few hours later I came up with this:
I’ve left transmitter on a desk and went for a walk. Even before leaving the building radio signal had to cross around 1 meter of bricks. Then travel through another building and only then go into the direction when I walked.
I must say: I was impressed. I still am. At 511 meters transmission was clear only when I was not blocking it with my body. Or standing near to metal fence. So I can safely assume: 500m is maximum range in densly populated urban area. On stock antennas and 100mW output power. Next week I will try stronger, dipole antennas.
My quest for ultimate (?) DIY telemetry system for UAVs continues. Last year I was playing with HC-12 433MHz wireless modules with pretty decent results. After all, more than 1km of range for a few bucks is more than acceptable. Still, HC-12 has at least few problems:
