Hello,
I have some problems with TPL communication (daisy chain) between MC33771C (2nd) and MCU (S32K344) (with MC33664), NXP's BCC driver is used.
When I use the nodes separately (only one node connected to MCU) everything is ok and works fine. But when I put them in a chain an configure the driver for 2 nodes, only the first node responds and the second one doesn't even wake up.
I tried to send a wake up pattern but I could not measure any signal on the Rx+/- (TPL output line of the MC33771C Chip) of the first node (see picture below).
Configurtion of the Driver:
Setup:
Can anyone tell me what is going wrong here?
Many thanks for your support in advance.
Best Regards
Hello JoDo,
thank you for the confirmation.
Have you assigned a specific address to each MC33771C?
On Power Up or POR, the first MC33771C device in the chain responds to address 00 0000b. The user must program the first device with a new address by writing to the INIT[CID] register. Programming the device with a new address allows the pack controller to communicate and initialize the next device in the daisy chain. Subsequent read/write commands to the next device must use the new address to
communicate.
With Best Regards,
Jozef
Hello @JozefKozon,
i use the NXP BCC driver and the function "BCC_Init(&gDrvConfig);" which does the assignment automatically.
While debugging, I found that the after reading the init register of the second node after its assignment, an error occurs. I guess that the second node has not received an assignment.
We designed our own board according to the MC33771C datasheet and initially could not establish TPL communication between the MC33664 and the MC33771C.
When were sending messages, there were resonance effects after the isolator . So we found out that the resonance came from the isolator in conjunction with 220pF capacitors. We removed the capacitors and put a differential resistor between RDTX+ and RDTX, the communication worked fine .
With Capcitors CBCC = 220pf | Withou Capcitors CBCC = 220pf |
Could our circuit adaptation lead to communication problems between the nodes?
What are the Cbcc capacitors for and how can we eliminate the resonance effects?
Best Regards,
JoDo
Hello JoDo,
so it looks like hardware issue. The recommended Cbcc capacitance for the MC33771C is 220pF. But The PROT ESD protection diode might add to the Cbcc capacitance. Have you used the recommended low capacitance bidirectional ESD protection diode?
Please also check the CTPL capacitor value. Recommended value is 68pF.
Please check section 3.2 in AN12605 for recommended common mode choke and section 3.3 for recommended ESD protection diode. Section 3.5 describes Layout recommendations. In the same AN12605 in section 4.3 signal ringings is described. Figure 12. looks similar to your scope you have taken.
The AN12605 can be downloaded from docstore, from this link:
https://www.docstore.nxp.com/products/product-hierarchy?query=AN12605#button-filter-group-kind:selec...paging:currentPage=0|paging:number=12
In the older MC33771C datasheet and in MC33771B datasheet and in other documents Cbcc recommended capacitance is 22pF.
With Best Regards,
Jozef
