I2C troubles.

temtronic · Posted: Wed Aug 08, 2018 5:55 am

Yes, GREAT, it's 'up and running'. I had a quick read of the datasheet while watching the rain finally come down here.
This is really what I call a 'smart' module, as it consists of a sensor AND a computer, so there's no low level driver instead talk to the onboard computer.
It makes sense that there is a WDT, clever to keep the module in a known state. There is a command to disable the WDT as well.

I also saw a command to Verify the module. Very handy as it flashes
an LED for you to confirm 'here I am, and I'm alive '!

The 'reset' command will reset ALL modules on the bus, so if you have say 6 of them, ALL will be reset, so it make take longer for the PIC to communicate to the sensors.

Now IF I only had a real use for the neat device.......
Too many PICs...too many Projects...too little time.

Jay

beaker404 · Joined: 24 Jul 2012 Posts: 163

I put the delay_us(2) in a precaution and will watch how transmissions go during testing. Seems to be ok for now.
I am now looking into getting more data out of the sensor. I am not getting the transmission speeds they claim, seems to be running about 15 HZ.

Right now my code is stripped to only do the loop I posted and send serial data at 19200. The send takes 6ms.

beaker404 · Joined: 24 Jul 2012 Posts: 163

Well I have a response from the vendor, they claim very high conversion rates for the sensor, I can only get about 25 HZ out of the sensor with a 16F876 @ 20MHz.

My basic loop is:

beaker404 · Joined: 24 Jul 2012 Posts: 163

The above loop takes 31.2ms to execute. Obviously 30ms of that is the delay. If I lower the delay, the code locks up.

Ttelmah · Joined: 11 Mar 2010 Posts: 19552

The speed you can get depends on the ranging mode selected. You can only get the 75Hz in the 'tinyLIDAR' mode with a 2m max range.
So how far do you need to sense?.
You will then need to set the range mode to suit, and adjust the time to suit this. 30mSec is required for the default mode (long range).

They don't say, but it is possible the device won't ACK if it is busy.
So try reading the ACK bit back from the address write, and wait till this is ready.

beaker404 · Joined: 24 Jul 2012 Posts: 163

Good suggestions, I did change the device mode to the tinylidar mode for the fastest response, but it did not change anything, perhaps the mode change did not take.

beaker404 · Joined: 24 Jul 2012 Posts: 163

The vendor claims the high data rates with an Arduino platform.

temtronic · Posted: Fri Aug 10, 2018 4:40 pm

You should be able to 'read back' the device's current configuration ( I read that as a command....).
I learned a long, long time ago to not just 'assume' that the command you send IS done, you MUST request and SEE the configuration.

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19552

The low latency reading requires you to switch to continuous mode (MC). Look at Appendix A in the data sheet.
The default mode takes 30mSec. The Tiny LIDAR mode reduces this to 18mSec. The continuous mode offers times down to just over 1mSec.

You have to understand what it does. In 'single shot', the D measurement, triggers it to make a new reading, and returns the value from the last one done. In continuous mode it carries on making readings all the time, and the data is available from it's buffer when you read.