Parallax Propeller Serial Port
I am trying to connect a Rapsberry pi to parallax Propeller microcontroller. My intend is to use the propeller read comands from the pi and control motors and read sensors and relay the information back to the Pi on a mobile robot. I intend to add vision eventually using OpenCV or some other vision library so the Usb port cannot be used for communications.
Any information regarding how to do the communications would be appreciated. Oh and one more thing my programming experiences are primarly C and Java with a little basic. The PI uses 3,3V levels on all its GPIO pins. Before I go on a little warning: Do not try to put hard (that is able do deliver lots of current) 5V levels on the PI, as you might succeed in lifting the PI's 3V3 supply up to 5V through the protection diodes embedded in GPIO pins, and putting 5V on the 3V3 line can destroy chips on the PI! So when you put a 5V signal on a PI GPIO pin, at least put a 1 series resistor in between the 5V driver and the GPIO pin, or better yet, divide the 5V signal to 3V with a resistor divider consisting of a 2K2 and a 3K3 resistor. But as the propeller is also a 3V3 powered chip it can be directly interfaced to a PI without any problems!
Digital signal levels are completely compatible. The Raspberry PI has many hardware assisted I/O capabilities, maybe the most obvious way to connect a raspberry PI and a Propeller is to use the UART, but do note that the boot software of the PI has assigned the UART port to a command terminal, if you want to use it for your own purposes you should program Linux to release the UART port before you can use it. Obviously SPI and I2C are other candidates, or you can use multiple parallel ports and built your own bit banged interface with them. I think you're looking at making the connection more complicated than it needs to be. You shouldn't need to deal with the GPIO at all. Instead just plug the Parallax Propeller into the USB port of the Raspberry Pi.
Or, plug it into a powered USB HUB and then into the Raspberry Pi. Most of the Propeller boards now and a built-in USB connection which uses an FTDI chip. This makes the Propeller board look like another serial port. You can then use that connection to download new code to the Propeller or you can use that serial (over USB) connection to send commands and data between the Raspberry Pi and the Propeller.
The Propeller is a great chip for handling the I/O. It is very flexible and can handle multiple things at once. The Raspberry Pi is great for the higher level stuff. I am going to use this setup on one of my own robots that already has a couple Propeller boards controlling it. The Raspberry Pi will give me a wireless LAN connection to the robot and also make it easier for the high level stuff. The interface is very similar to the Raspberry Pi to Arduino example in this months MagPi issue. Unfortunately as explained in my first post, the sole purpose of adding the Pi to my robot is to use open CV or some other vision library that propeller simply could not run, which means likely I am going to use a web cam were are primarily as far as I know usb based.
Is there a way to address multiple devices connected through a single usb port via usb hub without increasing the complexity of the code too much? If so I would like an example of this, in the C family of programming languages preferably. Although its in C basically this is for a completely different architecture, so will probably do you no good at all, at least not directly! That is because there most probably is suitable, very similar, driver code available already, fo example if you use python there probably is an existing library to add UART functionality to python, and for many jobs you could even use one of the existing Linux terminal emulator application program, if only to test the connection.
The main task you have is finding out how to take over the existing code that uses the UART for a SSL link with Linux, so that you can use a terminal to log into the linux running on the PI. You need to take over (disable) that code so that your own code can use the UART.
Parallax Propeller Serial Port Number
Perhaps this helps: I2C is nice, and can potentially be faster than UART but it needs a 'master' 'slave' setup, so either the PI or the Propeller needs to manage (initiate) all transfers (for both ways). If that isn't a problem (depending on use) then great, otherwise using the UART might be better. One fix is to make a GPIO on the slave and 'altert, I need output' pin, and connect it to a similar pin on the master, so that it becomes aware that the save device needs a transfer. Display posts from previous: Sort.