4 Replies Latest reply on Jun 27, 2016 10:10 AM by user_1377889

    I2C lockup on power up

    dschild

      Just wanted to run a scenario by you that is causing me some grief. I have a brd with a cy8c4247lqi-bl453 talking to an accelerometer (MMA8451) through I2C. The circuit is powered from a coin cell (CR2032) and the cypress chip is the master. I am using P1.4 and P1.5 for I2C. If I program the chip from the miniprog the I2C will start as soon as the chip is done programming and will run fine as verified by my scope. As soon as I try to run the device from battery with the miniprog disconnected the I2C locks up, both SCLK and Data go high. The chip is running because I am toggling one of the cypress pins and it is cycling. For some reason the I2C is getting hung up under battery supply. BTW, I also replaced the battery with my bench supply and had the same issue so I don’t think it is a supply issue because the chip is running. Any ideas?