Hi all,
I am currently working with TRF7960 and LM3S6950
I have a problem of writing and reading back a register after Power on.
In the firwmare, after power on and setting up clock and peripherals (GPIO, SSI, etc), it writes the address of 0x0B and then output clock pulses to read its value (the deafult value of 0x0B register is 0x87)
I check the waveform of SPI bus and it is correct (TCK, SS, MOSI) but there is no response from MISO pin (MISO should return 0x87)
The picture file is the waveform that I capture.
,
Line7 = TCk, Line6 = SS, Line5 = MISO, Line4 = MOSI, Line3 = EN
Because it reads 0x0B => it will write 0x4B to TRF7960 and then write a dummy data to pulse clocks and read back value from TRF7960 (but Line5 is alway 0s in my case !!!)
It can be checked that the polarity of TCK has been changed to falling edge capture for reading.
Note: I use the reference schematic described on page 10 of the datasheet of TRF7960 but I use 3.3V for both the MCU and TRF7960's VIN pin.
I also check output voltage of internal regulators of TRF7960, they are correct (VDD_A=2.7V, VDD_RF=3.2V,VDD_PA=3.2V,VDD_X=2.6V)
Could anyone help me what should I check or whether I need to configure TRF7960 before reading or writing its registers ?
Thanks
Huy