Sharing spi pins of ADS1299

sss0sohrabsss0sohrab iran,mashhad
edited August 2016 in Other Platforms
I Designed A schematic similar to OpenBCI project, but with the difference of Microcontroller (ATMega2560 instead of ATMega328) and another voltage level shifter (TXB0108 instead of SN74LVCC3245). There is a noticeable point that for programming microcontroller i used the same SPI pins that were connected to level shifter for communicating with ADS1299. After manufacturing my board it started working but after couple of times all the data that i received was 1.all of the registers were 0xFF and all of data were 0xFFFFFF and the SPI pins of level shifter (MOSI,MISO,SCLK) at 3.3V side, Are not working anymore. Is ADS1299 damaged? Is sharing SPI path between ADS1299 and programmer and Microcontroller wrong?
i Attached my schematics for further information.image

Comments

  • biomurphbiomurph Brooklyn, NY
    I don't see how sharing the SPI bus with the ADS1299 is causing your problem. When we made the 8bit board with the ATmega328, we had all of the parts on the board when we burned the Arduino bootloader (which uses the SPI bus).
    Perhaps the level shifter you're using is blown? Can you scope the lines to trace the issue?


  • sss0sohrabsss0sohrab iran,mashhad
    YES I Scoped the lines and the problem is that level shifter has blown too (at 5V side i have SPI clock but at the other side i don't have it anymore) but after that, i detached it from the board and i used a 3.3V arduino board for direct testing of the ADS1299 .but the problem remained .and apparently there is no reason for blowing of the level shifter except shared path of the avr programmer and microcontroller and ADS1299 .the point is that i program microcontroller with arduino through IDC connector.and as i said before it worked a couple of times but after that it started with returning of 1 for every data . i think both (ADS1299 and level shifter) has blown but i am not sure why?
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