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 ?
I want to add more info about my circuit:
- The MCU does not use SYS_CLK from TRF7960, it has a crystal of 8MHz
- The SPI frequency is 1MHz
I use SSI1 to interface with TRF7960
The code to read register 0x0B of TRF7960:
CLEAR_TRF_CS_n; SSI1_DR_R = 0x4B; // write address to read reg 0x0B while(SSI1_SR_R & SSI_SR_BSY); temp = SSI1_DR_R; SSI1_CR1_R &= ~SSI_CR1_SSE; // disable SSI module to change clock polarity for reading SSI1_CR0_R &= 0xFFFFFF3F; // clear SPH-SPO bits of CR0 register SSI1_CR0_R |= 0x00000080; // change SPH-SPO to 10 SSI1_CR1_R |= SSI_CR1_SSE; // enable SSI module SSI1_DR_R = 0x55; while(SSI1_SR_R & SSI_SR_BSY); reg= SSI1_DR_R; // store the read value SSI1_CR1_R &= ~SSI_CR1_SSE; // disable SSI module to change back clock polarity SSI1_CR0_R &= 0xFFFFFF3F; // clear SPH-SPO bits of CR0 register SSI1_CR1_R |= SSI_CR1_SSE; // enable SSI module SET_TRF_CS_n;
After you raise the EN line, did you verify that your 13.56MHz crystal is running? also - you can check the Bandgap voltage which should be 1.6VDC.
If you are using the LM3S line of Stellaris MCUs, then i would recommend that you go request the firmware project example we have available for the TRF7960 + LM3S9B96. This would be probably most helpful to you as an example for the SPI w/SS firmware steps, which in this case (with the TRF7960), as you know, do require a polarity change between writes on MOSI line and reads on the MISO line.
Also, below is example of writing register 0x09 and then the ISO Control Register.
Then here we are showing a write continuous on registers 0x00 to 0x0B
and continuous read
---------------------------------------------------------------------------------------------------------Please click the Verify Answer button on this post if it answers your question.---------------------------------------------------------------------------------------------------------
Thank you very much for your support.
I will request the firmware for my reference.
I also checked BAND_GAP pin and it was 1.6V as you said => It means that the 13.56MHz is running correctly, doesn't it?
So, TRF7960 does not need any set up in order to make it in operation, is it right ?
=> Just power up and then I can read/write its registers.
If it is so, I have no idea how to solve the problem because the waveform is correct (TCK, SS, MOSI) and all pins of TRF7960 are probed and their values seem to be correct but MISO has no signal only !!!! @_@
Here are the values of all pins I probed by my VOM:
Pin Value Pin Value Pin Value Pin Value
1 2.67V 9 0V 17 0V 25 0V
2 3.23V 10 0V 18 3.2V 26 1V
3 3.2V 11 1.6V 19 3.2V 27 1.3V
4 3.2V 12 0V 20 0V 28 3.2V
5 0V 13 0V 21 0V 29 0V
6 0V 14 0V 22 0V 30 1.2V
7 0V 15 0V 23 0V 31 1.2V
8 1.6V 16 2.6V 24 1V 32 2.6V
I also test all pin contacts of TRF7960 to the board by:
- Measuring Ohm between GND and the footpint pad of every pin => each pad will have an amount of resistance to the ground if its pin is in contact
=> All pads except gnd pads are OK (no infinite OHM occurs)
- Measuring Ohm between adjacent pads => short circuit between adjacent pads can be detected
=> No 0 ohm occurs => no short between pads
=> I think that TRF7960 has good contact to the board
Could you please suggest what should I do next to solve the problem ?
I checked the output pulses at SYS_CLK after power on, it seems to be incorrect because its frequency is just 30kHz not 60kHz or high frequency clock
According to the datasheet of TRF7960 on page 14, it says that when EN is hight, SYS_CLK will switch from 60kHz to 13.56MHz.
But in my case, SYS_CLK is just about 30kHz while EN is high.
Does it mean that the TRF7960 is malfunctioned ?
I want to update that I also checked pin 32 of TRF7960 (OSC_OUT) and there is a 13.56MHz clock
So I think the crystal is working.
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.