Pull up or down resistor SPI

[valdev]

Hello, I am doing some dev on the NRF51822 with a Cortex MO manager. I have trouble on the MISO pin, and I am wondering if I have to drive this MISO pin by any kind of pull up or down resistor. Thanks for you help

[Charles Manning]

You will need to explain more... What do you mean by "having trouble"?

When the slave is selected then it is supposed to be driving the line low/high.

[testy]

When nRF51 acts as master and slave is NOT selected, a slave's output is in a high impedance, so master's MISO input line won't have defined level and higher current (~tens of microamper, transient) consumption occurs.

Solution for nRF51 MISO input:

1. use nRF51 internal pull resistor or
2. disconnect input pin

[valdev]

Thanks for your answer. It s true I should describe a little bit more my dev

I am using the spi_master_example_with_slave_main main.c example from Nordic. I did some changes in order to avoid the error transfert and to send my own sequence several times. When I trig all the pins I get my clock cycles (3.3 Vpp) I expect, the CS is good (3.3V and 0V), I get an answer from my slave. On the MOSI pin I have a signal looks likes my clock with a 500mV pic pic and not my sequence!