NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

bryanhsieh — Thu, 15 Jun 2017 13:44:22 GMT

Thank you so much for answering all the questions, I think I will follow your suggestion and use an output to tell mcu to set spi to tri.

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

Sigurd — Thu, 15 Jun 2017 13:23:06 GMT

Leaking power into a pin while the power is off could potentially cause the current to leak into VDD via internal clamping diodes on the pin (or ESD protection diodes). You could potentially be powering the chip through a GPIO, so this should be avoided.

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

bryanhsieh — Thu, 15 Jun 2017 13:15:48 GMT

Hi thanks for the suggestion. Do you have any idea why as to why the problem still exists even when the board is not powered? Because originally I was thinking of putting a diode on Vdd to stop C232 from powering the board, so when it is downloading data only the nand flash is powered.

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

Sigurd — Thu, 15 Jun 2017 13:01:27 GMT

Q: If I am correct when spi is not used the chip defaults back to all pins in tri state?

A: No, If you have initalized the SPI, the SCK pin will be a output pin and the pin is therefore not in the default configuration(=high impedance mode). Even if you call nrf_drv_spi_uninit(), I belive you have to manually set the SPI pins to the default configuration with nrf_gpio_cfg_default(pin) afterwards.

Maybe the solution with the output from the C232 cable is the easiest? When a input pin on the nRF is pulled down/up, you make sure that the nRF disables the SPI and that the pins are set to the default configuration.

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

bryanhsieh — Thu, 15 Jun 2017 12:26:00 GMT

To Sigurd,

Hi thanks for the quick response. Even when the pca10040 is not powered I am still getting errors when inquiring the NAND flash id ( should be 2C36 but I am getting 10A1), if I dont share SCK then I get the correct id. If I am correct when spi is not used the chip defaults back to all pins in tri state? As when it is powered but running an example that doesnt use the spi peripheral, sharing spi seems to be working.

So should I use a mux in between or should I use an output from the C232 cable to tell the mcu to put all spi lines to tri?

RE: NRF52832 Sharing SPI Lines with FTDI SPI-USB Bridge

Sigurd — Thu, 15 Jun 2017 11:01:38 GMT

Hi,

You should not have any voltage on the I/O pins when the chip is not powered. When sharing the SPI lines with another master, it’s recommend to put the SPI pins in the default configuration when the other master is being used. See this post for more information about that.