Carl
Member
Hi, noob here...
I need to connect two OLIMEXINO-STM32 so I can send a couple of ints per second. The best way I have found is to use rs232 but I have not found any tutorial. There is a library for arduino called easyTransfer which seams perfect but it doesent work on the OLIMEXINO.
Can anyone help me? I simply want to be able to push a button and light both on_board_led on OLIMEXINO 1 and 2.
Would be very happy if anyone helped me.
//Carl
gbulmer
Moderator
Carl assuming you know a little bit about this stuff ...
RS232 is a standard which requires 12V. Don't bother if you only need to communicate over a metre or two. Converting to RS232 signal levels just introduces extra complexity.
Instead use the same protocol using the STM32F's USARTs, but at 3.3V, which requires very little other electonics.
1 Connect USARTs together: http://leaflabs.com/docs/usart.html
Rx of one USART to the Tx of the other, and vice versa. That page tells you which pins go where, on a Maple.
The Olimexino documentation http://www.olimex.com/dev/DUINO/OLIMEXINO-STM32/OLIMEXINO-STM32.pdf
tells you which pins are USART pins (e.g. CON3 has USART 2, and CON3+CON4 have USART 1)
I'd probably put a 100ohm resistor in each wire to reduce the danger of accidental shorting wires or misconnecting wires.
2. Use the Serial library: http://leaflabs.com/docs/lang/api/serial.html#lang-serial
to configure and transfer data.
(Full disclosure: I am not a member of LeafLabs staff)
MelonFarmer
Member
Hi,
I have tried a great deal to connect using SPI and have had no luck. From what I've read maple does not properly support making a board a slave. I've tried setting slave select pins manually as well as a whole other list of things. My probelm is my Master can send to my slave, and the slave can receive, however whenever I try to send from the slave to the master, the slave write just blocks. Hopefully i'm just missing something silly. I am also using olimexino boards.
gbulmer
Moderator
MelonFarmer - "... whenever I try to send from the slave to the master, the slave write just blocks"
I'm not sure what you mean.
AFAIK, the master can receive from a slave, but a slave can't send, because it can't initiate the transfer. Only the master can drive the clock.
You could use another pin (or two) to signal that it must turn master to slave, and slave to master. You'd have to write the code to do all of that.
Is this bi-directional and asynchronous? If it is, then UART to UART (Serial) might be a good way to go.
MelonFarmer
Member
Oh if that's the case I guess that settles it. I am already using serial just fine and dandy but I wanted to free up the serial for other things. SPI is quite a bit faster as well. I was confused as in the language guide there is a transfer function, so I figured the master must be reading off the slave, I thought that the MISO pin was for that. Thanks for responding so quick.
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