This section is about demos to interface the SBC with the AT324 and test serial communication and commands
The Latte Panda Mu and the Lite Carrier boards have a number of serial interfaces
I need to find out how they are mapped to linux ubuntu and how to use them
ttySxxx should be serial interfaces, on the pi they are also mapped to ttyAMAxxx
sona@sona-lp-n100-8gb:~$ ls /dev/
autofs i2c-7 nvme0 tty24 tty59 ttyS6
block i2c-8 nvme0n1 tty25 tty6 ttyS7
btrfs-control i2c-9 nvram tty26 tty60 ttyS8
bus initctl port tty27 tty61 ttyS9
char input ppp tty28 tty62 udmabuf
console kmsg psaux tty29 tty63 uhid
core kvm ptmx tty3 tty7 uinput
cpu log pts tty30 tty8 urandom
cpu_dma_latency loop0 random tty31 tty9 userfaultfd
cuse loop1 rfkill tty32 ttyprintk userio
disk loop10 rtc tty33 ttyS0 vcs
dma_heap loop11 rtc0 tty34 ttyS1 vcs1
dri loop2 shm tty35 ttyS10 vcs2
drm_dp_aux0 loop3 snapshot tty36 ttyS11 vcs3
ecryptfs loop4 snd tty37 ttyS12 vcs4
fb0 loop5 stderr tty38 ttyS13 vcs5
fd loop6 stdin tty39 ttyS14 vcs6
full loop7 stdout tty4 ttyS15 vcsa
fuse loop8 tpm0 tty40 ttyS16 vcsa1
gpiochip0 loop9 tpmrm0 tty41 ttyS17 vcsa2
hidraw0 loop-control tty tty42 ttyS18 vcsa3
hidraw1 mapper tty0 tty43 ttyS19 vcsa4
hpet mcelog tty1 tty44 ttyS2 vcsa5
hugepages mei0 tty10 tty45 ttyS20 vcsa6
hwrng mem tty11 tty46 ttyS21 vcsu
i2c-0 mmcblk0 tty12 tty47 ttyS22 vcsu1
i2c-1 mmcblk0boot0 tty13 tty48 ttyS23 vcsu2
i2c-10 mmcblk0boot1 tty14 tty49 ttyS24 vcsu3
i2c-11 mmcblk0p1 tty15 tty5 ttyS25 vcsu4
i2c-12 mmcblk0p2 tty16 tty50 ttyS26 vcsu5
i2c-13 mmcblk0rpmb tty17 tty51 ttyS27 vcsu6
i2c-14 mqueue tty18 tty52 ttyS28 vfio
i2c-15 mtd tty19 tty53 ttyS29 vga_arbiter
i2c-2 mtd0 tty2 tty54 ttyS3 vhci
i2c-3 mtd0ro tty20 tty55 ttyS30 vhost-net
i2c-4 net tty21 tty56 ttyS31 vhost-vsock
i2c-5 ng0n1 tty22 tty57 ttyS4 zero
i2c-6 null tty23 tty58 ttyS5 zfs
The library is pyserial if you try to access ports on Linux it will fail
Failed to open /dev/ttyS4: [Errno 13] could not open port /dev/ttyS4: [Errno 13] Permission denied: '/dev/ttyS4'
You need to give permission from your USER to the ports.
Commands let you see what the premission group is
Ubuntu Desktop
PermissionError: [Errno 13] Permission denied: '/dev/ttyS1'
sona@sona-lp-n100-8gb:~$ ls -l /dev/ttyS0
crw-rw---- 1 root dialout 4, 64 Sep 21 09:09 /dev/ttyS0
Ubuntu Server
sona@lpmu8gb:~$ ls -l /dev/ttyS0
crw------- 1 sona tty 4, 64 Nov 23 11:11 /dev/ttyS0
Permission for those ports is group dialout, so I add those permissions to my user
sudo usermod -a -G dialout $USER
sudo reboot
With that access to ports from user is allowed.
Remember that /dev/ttyS0 is the port that Ubuntu uses for the serial console
Under windows I'm free to give the baud rate I want, I tested 250Kb/s.
Under Linux it behaves differently. There seems to be a discretization of baud for no good reasons. I know the Intel hardware can do 250Kb/s under windows, but under Linux if I request that it does 9600 b/s.
I need to request likely from this table I found in pyserial for posix.
Right now I selected 115200b/s on Linux
#serialposix.py:96
BAUDRATE_CONSTANTS = {
0: 0o000000, # hang up
50: 0o000001,
75: 0o000002,
110: 0o000003,
134: 0o000004,
150: 0o000005,
200: 0o000006,
300: 0o000007,
600: 0o000010,
1200: 0o000011,
1800: 0o000012,
2400: 0o000013,
4800: 0o000014,
9600: 0o000015,
19200: 0o000016,
38400: 0o000017,
57600: 0o010001,
115200: 0o010002,
230400: 0o010003,
460800: 0o010004,
500000: 0o010005,
576000: 0o010006,
921600: 0o010007,
1000000: 0o010010,
1152000: 0o010011,
1500000: 0o010012,
2000000: 0o010013,
2500000: 0o010014,
3000000: 0o010015,
3500000: 0o010016,
4000000: 0o010017
}
There is an issue with speed on the microcontroller, there I do have coarser discretization because of clock speed and UART hadware, I can select 113636 and it is compatible with 115200.
//56818
//#define UART_UBRR 23
//113636
#define UART_UBRR 10
//125000
//#define UART_UBRR 9
//138888
//#define UART_UBRR 8
//156 250
//#define UART_UBRR 7
//250 000
//#define UART_UBRR 4
It's 20MHz / 16 / (UBRR+1). There is a fast mode, setting the prescaler to 8, but it halves the sampling and can result in more errors.
I'll need to go faster for the final application, targeting 500Kb/s.
A trick to test the SBC communication is to do a jumper and do loopback, so it removes the speed mismatch. It's useful to debug if the problem is in software, in this case it wasn't.
Install virtual environment for python
sudo snap install astral-uv --classic
sona@lpmu8gb:~/Demo 2 - Serial Communication SBC$ sudo snap install astral-uv --classic
2025-11-23T09:38:36Z INFO
Waiting for automatic snapd
restart...
astral-uv 0.9.5 from Alex Lowe (lengau) installed
Make sure you create a folder for the pythoin demos to run
sudo mkdir demo_serial_communication
cd demo_serial_communication
TODO: How do I clone just some of the code? Perhaps I do a release?
The most convenient way for it to autogenerate the virtual environment is to generate a toml project file and run uv with the command uv run
This will make sure that with a single line a venv is created with the right python version and dependencies
pyproject.toml
[project]
name = "demo_serial_communication_sbc_electronics"
version = "0.1.0"
requires-python = ">=3.13"
dependencies = [
"pyserial",
]Now, the first application tests the ports enumerated in /dev that are serial ports
demo_1_enumerate_serial.py
import serial
print(serial.__file__)
import serial.tools.list_ports
ports = serial.tools.list_ports.comports()
for port in ports:
print(port.device)
Execute the script
uv run demo_1_enumerate_serial.py
The first run will create .venv with the local libraries and interpreter and execute. In this screen I displayed the location of the library to make sure it's executing from .venv
uv run demo_1_enumerate_serial.py
Using CPython 3.14.0
Creating virtual environment at: .venv
Installed 1 package in 16ms
/home/sona/Demo 2 - Serial Communication SBC/.venv/lib/python3.14/site-packages/serial/__init__.py
/dev/ttyS31
/dev/ttyS30
/dev/ttyS29
/dev/ttyS28
/dev/ttyS27
/dev/ttyS26
/dev/ttyS25
/dev/ttyS24
/dev/ttyS23
/dev/ttyS22
/dev/ttyS21
/dev/ttyS20
/dev/ttyS19
/dev/ttyS18
/dev/ttyS17
/dev/ttyS16
/dev/ttyS15
/dev/ttyS14
/dev/ttyS13
/dev/ttyS12
/dev/ttyS11
/dev/ttyS10
/dev/ttyS9
/dev/ttyS8
/dev/ttyS7
/dev/ttyS3
/dev/ttyS2
/dev/ttyS1
/dev/ttyS6
/dev/ttyS5
/dev/ttyS4
/dev/ttyS0
In the Latte Panda Mu Lite Board, serial port S0 is the debug interface that is connected by GRUB to the linux serial terminal
While S4 to S6 are three serial ports available to user, I diagnosed them with an oscilloscope and terminal to make sure they work
TODO: add documentation for the serial ports here?
uv run demo_2_ask_signature.py
Output if user lacks permission for dialout
$ uv run demo_2_ask_signature.py
/home/sona/Demo 2 - Serial Communication SBC/demo_2_ask_signature.py:18: SyntaxWarning: "\D" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\D"? A raw string is also an option.
(ToB) F:\Data\Project\Project OrangeBot\RAMIE-RAD_AI_Messing_In_Earthworks\Software\Demo 1 - Serial Communication>python demo_2_ask_signature.py
Failed to open /dev/ttyS31: [Errno 13] could not open port /dev/ttyS31: [Errno 13] Permission denied: '/dev/ttyS31'
Failed to open /dev/ttyS30: [Errno 13] could not open port /dev/ttyS30: [Errno 13] Permission denied: '/dev/ttyS30'
Failed to open /dev/ttyS29: [Errno 13] could not open port /dev/ttyS29: [Errno 13] Permission denied: '/dev/ttyS29'
Failed to open /dev/ttyS28: [Errno 13] could not open port /dev/ttyS28: [Errno 13] Permission denied: '/dev/ttyS28'
Failed to open /dev/ttyS27: [Errno 13] could not open port /dev/ttyS27: [Errno 13] Permission denied: '/dev/ttyS27'
Failed to open /dev/ttyS26: [Errno 13] could not open port /dev/ttyS26: [Errno 13] Permission denied: '/dev/ttyS26'
Failed to open /dev/ttyS25: [Errno 13] could not open port /dev/ttyS25: [Errno 13] Permission denied: '/dev/ttyS25'
Failed to open /dev/ttyS24: [Errno 13] could not open port /dev/ttyS24: [Errno 13] Permission denied: '/dev/ttyS24'
Failed to open /dev/ttyS23: [Errno 13] could not open port /dev/ttyS23: [Errno 13] Permission denied: '/dev/ttyS23'
Failed to open /dev/ttyS22: [Errno 13] could not open port /dev/ttyS22: [Errno 13] Permission denied: '/dev/ttyS22'
Failed to open /dev/ttyS21: [Errno 13] could not open port /dev/ttyS21: [Errno 13] Permission denied: '/dev/ttyS21'
Failed to open /dev/ttyS20: [Errno 13] could not open port /dev/ttyS20: [Errno 13] Permission denied: '/dev/ttyS20'
Failed to open /dev/ttyS19: [Errno 13] could not open port /dev/ttyS19: [Errno 13] Permission denied: '/dev/ttyS19'
Failed to open /dev/ttyS18: [Errno 13] could not open port /dev/ttyS18: [Errno 13] Permission denied: '/dev/ttyS18'
Failed to open /dev/ttyS17: [Errno 13] could not open port /dev/ttyS17: [Errno 13] Permission denied: '/dev/ttyS17'
Failed to open /dev/ttyS16: [Errno 13] could not open port /dev/ttyS16: [Errno 13] Permission denied: '/dev/ttyS16'
Failed to open /dev/ttyS15: [Errno 13] could not open port /dev/ttyS15: [Errno 13] Permission denied: '/dev/ttyS15'
Failed to open /dev/ttyS14: [Errno 13] could not open port /dev/ttyS14: [Errno 13] Permission denied: '/dev/ttyS14'
Failed to open /dev/ttyS13: [Errno 13] could not open port /dev/ttyS13: [Errno 13] Permission denied: '/dev/ttyS13'
Failed to open /dev/ttyS12: [Errno 13] could not open port /dev/ttyS12: [Errno 13] Permission denied: '/dev/ttyS12'
Failed to open /dev/ttyS11: [Errno 13] could not open port /dev/ttyS11: [Errno 13] Permission denied: '/dev/ttyS11'
Failed to open /dev/ttyS10: [Errno 13] could not open port /dev/ttyS10: [Errno 13] Permission denied: '/dev/ttyS10'
Failed to open /dev/ttyS9: [Errno 13] could not open port /dev/ttyS9: [Errno 13] Permission denied: '/dev/ttyS9'
Failed to open /dev/ttyS8: [Errno 13] could not open port /dev/ttyS8: [Errno 13] Permission denied: '/dev/ttyS8'
Failed to open /dev/ttyS7: [Errno 13] could not open port /dev/ttyS7: [Errno 13] Permission denied: '/dev/ttyS7'
Failed to open /dev/ttyS3: [Errno 13] could not open port /dev/ttyS3: [Errno 13] Permission denied: '/dev/ttyS3'
Failed to open /dev/ttyS2: [Errno 13] could not open port /dev/ttyS2: [Errno 13] Permission denied: '/dev/ttyS2'
Failed to open /dev/ttyS1: [Errno 13] could not open port /dev/ttyS1: [Errno 13] Permission denied: '/dev/ttyS1'
Failed to open /dev/ttyS6: [Errno 13] could not open port /dev/ttyS6: [Errno 13] Permission denied: '/dev/ttyS6'
Failed to open /dev/ttyS5: [Errno 13] could not open port /dev/ttyS5: [Errno 13] Permission denied: '/dev/ttyS5'
Failed to open /dev/ttyS4: [Errno 13] could not open port /dev/ttyS4: [Errno 13] Permission denied: '/dev/ttyS4'
Testing port: /dev/ttyS0
Output if user has permission for dialout, but I had a problem of not receiving
sona@lpmu8gb:~$ cd Demo\ 2\ -\ Serial\ Communication\ SBC/
sona@lpmu8gb:~/Demo 2 - Serial Communication SBC$ uv run demo_2_ask_signature.py
/home/sona/Demo 2 - Serial Communication SBC/demo_2_ask_signature.py:18: SyntaxWarning: "\D" is an invalid escape sequence. Such sequences will not work in the future. Did you mean "\\D"? A raw string is also an option.
(ToB) F:\Data\Project\Project OrangeBot\RAMIE-RAD_AI_Messing_In_Earthworks\Software\Demo 1 - Serial Communication>python demo_2_ask_signature.py
Failed to open /dev/ttyS31: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS30: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS29: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS28: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS27: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS26: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS25: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS24: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS23: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS22: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS21: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS20: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS19: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS18: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS17: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS16: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS15: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS14: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS13: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS12: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS11: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS10: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS9: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS8: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS7: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS3: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS2: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS1: Could not configure port: (5, 'Input/output error')
Testing port: /dev/ttyS6
Testing port: /dev/ttyS5
Testing port: /dev/ttyS4
Testing port: /dev/ttyS0
I closed the cable with a jumper to test problems, no problems. It turns out it was speed under linux.
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'SIGN\x00'
Testing port: /dev/ttyS4
Connected the electronics
I moved application to 115200 b/s I moved the firmware to 113636 b/s Now it communicates fine. I'll need to significantly accelerate the communication for the future
esting port: /dev/ttyS4
Response from /dev/ttyS4: b'RAMIE\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'RAMIE\x00'
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'RAMIE\x00'
Testing port: /dev/ttyS4
Works really well, it finds a serial port that answer with something, and uses that to communicate with the board
sona@lpmu8gb:~/Demo 2 - Serial Communication SBC$ uv run demo_4_serial_direct_speed.py
Failed to open /dev/ttyS31: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS30: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS29: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS28: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS27: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS26: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS25: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS24: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS23: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS22: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS21: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS20: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS19: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS18: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS17: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS16: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS15: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS14: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS13: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS12: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS11: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS10: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS9: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS8: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS7: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS3: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS2: Could not configure port: (5, 'Input/output error')
Failed to open /dev/ttyS1: Could not configure port: (5, 'Input/output error')
Testing port: /dev/ttyS6
Testing port: /dev/ttyS5
Testing port: /dev/ttyS4
Response from /dev/ttyS4: b'RAMIE\x00'
Testing port: /dev/ttyS0
Responsive ports:
/dev/ttyS4
Connected to /dev/ttyS4. Press any key to stop...
Sent: b'VR1L0\x00'
Sent: b'VR2L0\x00'
Sent: b'VR3L0\x00'
Sent: b'VR4L0\x00'
Sent: b'VR5L0\x00'
Sent: b'VR6L0\x00'
Sent: b'VR7L0\x00'
Sent: b'VR8L0\x00'
Sent: b'VR9L0\x00'
Sent: b'VR10L0\x00'
Sent: b'VR10L0\x00'
Sent: b'VR9L0\x00'
Sent: b'VR8L0\x00'
Sent: b'VR7L0\x00'
Sent: b'VR6L0\x00'
Sent: b'VR5L0\x00'
Sent: b'VR4L0\x00'
Sent: b'VR3L0\x00'
Sent: b'VR2L0\x00'
Sent: b'VR1L0\x00'
Sent: b'VR0L0\x00'
Sent: b'VR-1L0\x00'
Sent: b'VR-2L0\x00'
wget https://github.com/B-AROL-O/RAMIE-RAD_AI_Messing_In_Earthworks/tree/Master/Software/Demo%201%20-%20Serial%20Communication%20Host
wget https://github.com/B-AROL-O/RAMIE-RAD_AI_Messing_In_Earthworks/archive/refs/heads/Master.zip -O repo.zip
sona@lpmu8gb:~$ wget https://github.com/B-AROL-O/RAMIE-RAD_AI_Messing_In_Earthworks/archive/refs/heads/Master.zip -O repo.zip
--2025-11-23 09:30:26-- https://github.com/B-AROL-O/RAMIE-RAD_AI_Messing_In_Earthworks/archive/refs/heads/Master.zip
Resolving github.com (github.com)... 140.82.121.4
Connecting to github.com (github.com)|140.82.121.4|:443... connected.
HTTP request sent, awaiting response... 404 Not Found
2025-11-23 09:30:26 ERROR 404: Not Found.