Saturday, 04 November 2017 08:52

Raspberry Pi serial console setup

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The serial console is an invaluable tool for setup and debugging if you’re working with embedded boards. For example you can use it to fix boot problems or to login to the board when keyboard, display and network are not available.
The Raspberry Pi has a serial peripheral accessible from the GPIO header that can be easily used for this purpose. Please remember that you'll need an interface to make the connection working because the logic levels of the Raspberry Pi Broadcom chip (0/3.3v) are not compatible with the standard RS232 serial port (-12/+12v) generally available on standard PCs. Furthermore, new generation computers are being shipped without a serial port, so in this case, the only solution it’s to use an USB to serial interface. I'm actually using one of those.


RS232 to TTL Adapters


As said before, the main function of these adapters is to interface the embedded board logical levels to the PC serial port ones and vice versa. 
Computers serial ports complies with the RS-232 telecommunications standard. RS-232 signals are similar the TTL serial signals in that they transmit one bit at a time, at a specific baud rate. The two differ solely at a hardware level.


In a RS-232 port a logic high 1 is represented by a negative voltage -12v , while for a logic low 0 is used a positive voltage +12v. In TTL instead a logic high is represented by the peripheral power supply voltage, which is often 1.8v, 3.3v or 5v; A logic low instead is represented by 0v. 
The higher voltages of an RS-232 signal help to make it less susceptible to noise, interference, and degradation. This means that an RS-232 signal can generally travel longer physical distances than their TTL counterparts.


The core of most of these adapters is a famous intengrated circuit called MAX232









My choose


I picked up on Amazon a SunFounder FT232RL FTDI USB to TTL Serial Adapter Module 3.3V 5V. It's a very versatile adapter since it can be configured with two operative voltages 3.3v and 5v, using a dip switch on the board side. So It can be used for a large number of applications. Obviously you can find a lot of good alternatives on internet. 

For the connections I choose a fast working solution : a female to female dupont cable. With this you can easily connect the two boards pin-strips without needing to make dedicated cables or to solder. Of course it's only doable for prototypes.


Read 756 times Last modified on Tuesday, 07 November 2017 22:21

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