Dangling UART1 TX Pin

I have build my own board for the TX2 module using this guide JetsonTX2_OEM_Product_DesignGuide but on my board it will not start, not even a trace of log from /var/log/syslog but it boots fine on the NVIDIA Developer Board.

When the TX2 boot on my board it is very slow it takes about 10 seconds for the CR2 (power) LED and the CR1 LED to light up as opposed to the NVIDIA Developer board where it is instant (<0.5seconds). What can be the root cause for this? I have found that the UART1_TX pin is dangling on my board, it is measuring 0V, not 1.8V as shown in Fig 41 (below) Jetson TX2 Strap Connections, in JetsonTX2_OEM_Product_DesignGuide. The power VDD_5V0_IO_SYS, VDD_3V3_SYS and VDD_1V8 on my board are normal.

Fig 41
https://ibb.co/mxsggJ

Hi, UART1_TX should be 0V as the pull-up is not used.

I don’t get clear info from your input…can it boot slowly or not with TX2 module + your board ?

Did you check the power up sequence (figure 3 in OEM DG) by measuring each signals as list?

Hi,Trumany.
UART1-TX is pulled up to 1.8V, should be 1.8V while booting.

Hi,PlantMaster.
Have your problem resolved? I meet the same problem.

UART1_TX should be 0v during boot as its pull-up is not mounted, please check OEM DG first.
Regarding this behavior, please check all strapping pins’ status, they should be same as guide.

Hi,Trumany.
I check the V20170501 of OEM DG, on page 66. UART1_TXD pin have a 4.7K PU and a ~100K PD,so this pin should be 1.8V. Do you have checked the V20170501 of OEM DG?

That 4.7K is dot line which means not mounted. Please check the latest version doc in DLC.

Hi,Trumany.
I have measured UART1_TXD pin voltage on tx2 dev kit board, it is 1.8V, not 0V. This means UART1_TXD pin is pulled up to 1.8V.

but in my custom board UART1_TXD pin is 0V, and it can not boot, UART0_TXD pin is always high.

It is low during power on to implement strapping function, and will be pulled up by level shift on carrier board after power on, your custom board has not this level shift. You can check schematic of carrier board for more info. Please do not waste time on this point and check all your other strapping pins status during power on to see if any problem.