Hi, For fun I'm trying to achieve communication between a linux master (raspberry pi) and an arduino slave over i2c. This somewhat works. Somewhat because for example I occasionally get a -1 return value on read(). What I'm doing is as follows: - i'm "sending messages" to the arduino using regular write() calls. I do a write with in one go all data (so not sending 1 message with multiple writes). commands are in size somewhere between 1 and 32 bytes - after I've send a message to the arduino, it'll collect some data from an other source and put this in a send-buffer. Later on the master will fetch this data. The amount of data to be transmitted to the master is not always the same. Sometimes 6 bytes, sometimes 1204 bytes. Not much more because of RAM limits in the arduino. - After a while (after sending the command to the arduino) I do a read() on the linux master to receive the data from the arduino. for this i have a 2KB buffer. so I do read(fd, buffer, 2048) Occasionally this read() returns a -1. My questions now are: - is what I'm doing here this supposed to work? e.g. sending messages in random size of 1...32 bytes (there's a 32 byte limit in the arduino for receiving), receiving data of random-size e.g. doing a read of 2KB and expecting that or less data - how can I see if there's a device listening on an i2c address? should I do a write and see if this write succeeds? wrap it in a poll(POLLOUT) first? - how can I see when I do a read() from a device, if there is data? do a poll(POLLIN) and then a read? - in what situations will the read() return a -1? if there are multiple situations: how can I see which situation triggered it? regards Folkert van Heusden -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
