I have a sensor hooked up to UART1. This seems to work just fine using cape-universal and config-pin to setup P9-24 and P9-26 in uart mode.
When I modify uEnv.txt to use BB-UART1 overlay, I am unable to read data from the sensor.
Relevant portions of uEnv.txt looks like this:
Don’t enable cape-universal
Enable UART1 and I2C1 overlays
And I have commented out the original cmdline:
#cmdline=coherent_pool=1M quiet cape_universal=enable
Slots look like this:
0: PF---- -1
1: PF---- -1
2: PF---- -1
3: PF---- -1
4: P-O-L- 0 Override Board Name,00A0,Override Manuf,BB-I2C1
5: P-O-L- 1 Override Board Name,00A0,Override Manuf,BB-UART1
Kernel and rootfs:
debian@bbb2:~$ uname -r
debian@bbb2:~$ cat /etc/dogtag
BeagleBoard.org Debian Image 2016-01-17
I have also pulled the latest bb.org-overlays and run install.sh.
I have this working on another system with 4.1.13-ti-r35 with the 2015-11-09 rootfs. If I am correct in analyzing the BB-UART1 dtb that is working on this system, it appears as if P9_24 is configured with a pulldown resistor and P9_26 is configured with a pullup resistor. The BB-UART1 dtb on the system where this is not work (and the current version from bb.org-overlays) has no pullup/pulldown resistors configured for those pins. Looking at cape-universal (that works), it appears as if P9_24 and P9_26 are both configured with pullups.
So, I’m assuming that this is why my current BB-UART1 setup is not working.
Is the configuration of the current BB-UART1 (actually all of them) without pullup/pulldown for UART mode by design? If so, why? And of course, the converse question for cape-universal.
Not being a H/W guy, maybe someone can inform me as to why my current BB-UART1 doesn’t work and why these dtb’s are thusly configured.