Raspberry Pi Forums

rzusman

I updated my Jessie install it Buster, and got a bunch of errors. Surprisingly, it actually boots and runs (mostly), but not all of my software is working, notably lirc. When I try a ‘sudo apt-get update’ I get the following error: Get:1 http://mirrordirector.raspbian.org buster InRelease [15.0 kB] ...

rzusman

At this point, you need an oscilloscope.

That’s the easiest way to see what signals are being generated - both to the input of the RS-485 board, and at it’s outputs.

rzusman

It's essentially impossible. The failure mode for a Flash cell is power-off data retention of less than 10 years. To read and write a cell until failure (cell won't retain the data between the read and write cycles, which might be an hour or so if you are writing the entire device) would take years,...

rzusman

Try flushing the input buffer before you transmit the character.

rzusman

You could always bit-whack it at any baud rate you want.
I2C is ugly, but I wrote a bit-whacked interface in assembly language decades ago, so it’s not impossible.

rzusman

You need something like this device: http://www.ti.com/lit/ds/slis128/slis128.pdf

This chip will do the voltage-shifting and signal buffering for you. You will still need to write some software to interpret and generate the LIN frames.

rzusman

I made an PWM LED dimmer for a friend’s art project, using a Silicon Labs processor. The 8-bit PWM looked fine, until the LEDs were very dim, and then the last 8-10 steps or so were very abrupt. When I used the 16-bit PWM, the fades were perfectly smooth, all the way to zero brightness. So, PWM gran...

rzusman

You need to re-think your circuit. Having the 5v regulator powered all the time is going to kill your battery. That regulator has something like 5mA or quiescent current. Also, you need to be careful about low-side switching. Once you pull the ground, your device naturally floats to Vcc, since the t...

rzusman

Don’t dismiss using a separate micro controller as a supervisor so fast...

You can get a tiny micro for a buck or so, and it can handle all the logic.

rzusman

Here’s what I did for my Compute Module design: I have a Supercap backup power supply that allows graceful shutdown. In your case, this would be your batteries. I use a separate micro controller to monitor the state of the supercap charge. Once they are fully charged, I enable my 3.3v and 5v switchi...

rzusman

You could use something like this: https://www.pololu.com/product/2971

And then connect the enable pin to a serial-in, parallel out shift register, or a port expander.

rzusman

Yes the module is able to boot with raspbian lite, but I thought that files (such as git clones) could be put on the compute module over the usb slave port? If you follow the instructions PhilE posted above, you should be able to mount the CM as two volumes. Then (from a Linux host), you can just c...

rzusman

It does not help me, I have the OS up and running. I just don't know how to install software on it. I want to use pip3 to install opencv. Since there is no internet connection, I am having issues. Wait. Do you mean that the CM is up and running? If so, get a USB-Ethernet converter, or a USB-WiFi do...

rzusman

Frankly, the DS1307 accuracy stinks.

Spend the extra money and get the DS3231, which is temperature compensated, and is guaranteed accurate to a a minute or so/year.

http://www.reuk.co.uk/wordpress/accurat ... to-ds1307/

rzusman

Raspbian IS Linux...

rzusman

At a clock speed of 1.4Ghz, that's 100 instructions (more or less). From C, using something like WiringPi, you should easily be able to toggle a pin that quickly. BUT: if you are doing this in Linux, there is a non-zero chance that your pulse will be stretched to some very long duration (10mS or mor...

rzusman

What scripting language are you using?
It would be pretty simple to do a brute-force check in Python.

rzusman

Have you ‘scoped the output? That’s the only way to be sure of the pulse rise time, width, and fall time.

rzusman

I’d be willing to bet that it’s impossible to generate a pulse that’s narrower than 3nS with a user-space program on the Pi.
Even at 1.4 GHz, that’s only around 4.2 clocks, and there’s going to be way more cycles than that with the function call overhead.

rzusman

You can create a system service that will re-launch a crashed process automatically.

https://medium.com/@benmorel/creating-a ... 1b5c8b91d6

This won’t fix a hung process - you need a watchdog for that.

rzusman

Your time must be worth more than a socket...

I could solder wires to the CM edge connector, but it would take hours to cut and strip all the wires and solder them. Also, the USB connector probably wouldn’t work with pigtail leads - it needs to be controlled impedance.

rzusman

Don't use a blocking read. Use something like select with a timeout.

Some discussion here: https://stackoverflow.com/questions/634 ... gracefully

rzusman

I just found a bug in my code, due to me not explicitly setting tm_isdst to -1 when updating the time using mktime. It took me a long time to detect, since I live in Arizona, and we don’t observe DST. Changing the time update routine to have tm_isdst = -1 seems to fix the time update issue I was hav...

rzusman

Thanks for the link, and I may experiment with it when I have the time, but I'm not sure it will do what I want. The RTS/CTS lines are controlled by the buffer state, as I understand it, and are not really what I want , which is a TE signal that is the exact width of one byte, including the start an...

rzusman

I use RS-485 on the CM3L. I am using a low baud rate (9,600), so my timing may not be as critical as yours, but I ended up manually controlling the TE input of the RS-485 driver (Enable TE, send data, disable TE). The only way I was able to do that was to put the driver thread to sleep for 10mS, jus...

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