As i need to check the console of a booting banana pi and i dont have a ttls to usb converter availabl, but have another bpi, i just connect both directly.
Using info available at Lemaker site, that i quote bellow, and its image as guide.
“The default serial port /dev/ttyS0 at MMIO 0x1c28000, used for (bootstrap) debugging and the serial console, is located at J11 – refer to the picture and instructions below.”
Just put:
- The black wire on both bpi in gnd,
- The white wire on one pi in txd, on the other in rxd,
- The green wire on one pi in rxd, on the other in txd,
cat /dev/ttyS0
Sample try booting minix on banana pi
U-Boot SPL 2014.04-10733-gbb5691c (Jul 08 2017 - 11:56:59) Board: BananaPi DRAM: 1024 MiB CPU: 960000000Hz, AXI/AHB/APB: 3/2/2 spl: not an uImage at 1600 U-Boot 2014.04-10733-gbb5691c (Jul 08 2017 - 11:56:59) Allwinner Technology CPU: Allwinner A20 (SUN7I) Board: BananaPi I2C: ready DRAM: 1 GiB MMC: SUNXI SD/MMC: 0 *** Warning - bad CRC, using default environment In: serial Out: serial Err: serial Net: dwmac.1c50000 Hit any key to stop autoboot: 0 reading uEnv.txt 810 bytes read in 22 ms (35.2 KiB/s) Loaded environment from uEnv.txt Running uenvcmd ... starting from MMC mmc - MMC sub system Usage: mmc read addr blk# cnt mmc write addr blk# cnt mmc erase blk# cnt mmc rescan mmc part - lists available partition on current mmc device mmc dev [dev] [part] - show or set current mmc device [partition] mmc list - lists available devices mmc setdsr - set DSR register value reading script.bin 50972 bytes read in 30 ms (1.6 MiB/s) reading kernel.bin 264580 bytes read in 41 ms (6.2 MiB/s) reading ds.elf 79852 bytes read in 31 ms (2.5 MiB/s) reading rs.elf 113152 bytes read in 28 ms (3.9 MiB/s) reading pm.elf 81024 bytes read in 31 ms (2.5 MiB/s) reading sched.elf 44520 bytes read in 29 ms (1.5 MiB/s) reading vfs.elf 182184 bytes read in 41 ms (4.2 MiB/s) reading memory.elf 2762932 bytes read in 185 ms (14.2 MiB/s) reading tty.elf 63428 bytes read in 35 ms (1.7 MiB/s) reading mib.elf 82600 bytes read in 31 ms (2.5 MiB/s) reading vm.elf 165788 bytes read in 40 ms (4 MiB/s) reading pfs.elf 56336 bytes read in 29 ms (1.9 MiB/s) reading mfs.elf 106368 bytes read in 32 ms (3.2 MiB/s) reading init.elf 318100 bytes read in 44 ms (6.9 MiB/s) console=tty02 rootdevname=c0d0p1 verbose=0 hz=1000 board_name= ## Starting application at 0x80200000 ... software interrupt pc : [<80200a40>] lr : [<80200a40>] sp : 80204fb8 ip : 00000041 fp : 00000000 r10: 00000003 r9 : 7fb66f0c r8 : 7ffbc724 r7 : 7fb7c480 r6 : 80200000 r5 : 00000003 r4 : 80205144 r3 : 8020a794 r2 : 00000000 r1 : 80205131 r0 : ffffffbf Flags: nZCv IRQs off FIQs off Mode SVC_32 Resetting CPU ... resetting ...