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SPI Master not working with Flash

eric ely

I am working with the nrf51822 eval kit and custom boards based on the Laird BL600 module. I am using SDK v5.2.

I am trying to connect to external Flash (Microchip SST25VF016B) through SPI 1. No matter what I do, the Flash returns 0xFF.

I have tried the nrf51822 SPI loopback example, it works fine. Indeed, I can loop back MISO<->MOSI and read the correct data. So the nrf51822 chip seems to be working, at least with itself.

I also took the Flash chip and hooked it to an Arduino Pro Mini. With that setup, I can talk to the Flash just fine. So I am pretty confident that the Flash works and that I am hooking it up correctly as I have the two rigs next to eachother for reference.

I have made sure the mode settings and frequency are the same between the Arduino and the nrf51822. Also, just to try it, I used many different mode/frequency combinations. Nothing works. No matter what I do, I always get back 0xFF on the MISO line with the nrf51822.

I don't have a scope, unfortunately, so I can't debug at that level.

Anyone have any idea what could be causing this? Any idea at all? I am wide open as I am pretty much stuck and have been trying everything.

I posted the code I am using for reference. Here is the Arduino test (which works and properly prints the Flash ID): gist.github.com/.../6fd9709f76584b8af792

Here is the nrf51822 test (which doesn't work, and just returns 0xFF every time): gist.github.com/.../2bedc0ce3f7e2251174d

For the nrf51822, I am using the provided spi_master class. I have thoroughly gone through this and not changed anything in there except the frequency.

  • 0

    I analyzed both of the SPI transfers for the two codes on an Arduino and the nRF51822. The only difference between them is that on the nRF51822 the SS pin is set high and low again between every byte transfer.

    Try to add a bool stop_condition as an argument to the spi_master_tx_rx() and change the last line in the function to this

    if(stop_condition){
    nrf_gpio_pin_set(SEL_SS_PINOUT);
}

    Now you can set the SS pin high after the last byte only.

  • 0

    Hi

    So you have your flash configured as SPI slave and are using the SPI master on the nRF51 (BL600), if I understand you correctly.

    Too bad you do not have a scope, that would be my first suggestion to debug the issue, to see what is the difference in output from the SPI master on the Arduino Pro Mini and the nRF51. As a cheaper option, I would recommend you to get a hold of logical analyzer, e.g. this one.

    You could perhaps set leds on your board when there is an activity on the SPI pins, just too see that it is actually having activity as expected. But the only good way is to measure the actual communication on the pins. You can then analyse the signals yourself and/or send a snapshot of the signal output to us for further analysis.

  • 0

    That was it. Wow, that was a pretty stupid mistake on my part. I spent hours pouring over the SPI spec and datasheets, and somehow I just missed that. Thanks for the extra eyes and spotting this!

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