How to write to a Characteristic as of Bluez 5.48 - linux

Question

I am using Bluez 5.50; 5.48 was the version acquire-write became officially (non-experimentally) supported. Am I using the acquire-write / write feature properly?
On my Raspberry Pi Zero W:
pi#raspberrypi:~ $ bluetoothctl
[bluetooth]# power on
Changing power on succeeded
[bluetooth]# scan on
Discovery started
[bluetooth]# connect B8:27:E8:72:33:7A
Attempting to connect to B8:27:E8:72:33:7A
Connection successful
[DSD TECH]# menu gatt
[DSD TECH]# select-attribute 0000ffe1-0000-1000-8000-00805f9b34fb
[DSD TECH:/service0010/char0011]# acquire-write
[CHG] Attribute /org/bluez/hci0/dev_B8_27_E8_72_33_7A/service0010/char0011 WriteAcquired: yes
AcquireWrite success: fd 7 MTU 23
[DSD TECH:/service0010/char0011]# write("h")
[DSD TECH:/service0010/char0011]# write('h')
[DSD TECH:/service0010/char0011]# write(h)
[DSD TECH:/service0010/char0011]# write(0x68)
On my Arduino Nano connected to HM-10:
void setup()
{
Serial.begin(9600);
}
void loop() {
delay(10);
if (Serial.available())
{
char c = Serial.read();
Serial.println("Read value");
}
}
I use the iOS app named "Serial" which connects to my HM-10. I send the letter h over and read "Read value" on the arduino serial monitor. I do this directly before and after using the raspberry pi, on the same arduino serial monitor. The raspberry pi notifications never come thru. Yes, I am certain it is the same HM-10. It is the only HM-10 I have powered on in BLE range, and I cannot connect to the UUID while my phone is connected. (Actually, I submit connect B8:27:E8:72:33:7A to the raspberry pi, and keeps trying, and then disconnect from phone, and rpi automatically connects).
Thanks in advance!

Answer 1

When using gatt services with bluetoothctl, leave off the parentheses and just use:
write 0x68

Answer 2

acquire-write returns a file descriptor that can be used for writing to the GATT characteristic, usage of write will be locked. so either use acquire-write (which requires a write-without-response flag) or use write.
void WriteValue(array{byte} value, dict options)
Issues a request to write the value of the
characteristic.
Possible options: "offset": Start offset
"device": Device path (Server only)
"link": Link type (Server only)
"prepare-authorize": boolean Is prepare
authorization
request
Possible Errors: org.bluez.Error.Failed
org.bluez.Error.InProgress
org.bluez.Error.NotPermitted
org.bluez.Error.InvalidValueLength
org.bluez.Error.NotAuthorized
org.bluez.Error.NotSupported
fd, uint16 AcquireWrite(dict options) [optional]
Acquire file descriptor and MTU for writing. Usage of
WriteValue will be locked causing it to return
NotPermitted error.
For server the MTU returned shall be equal or smaller
than the negotiated MTU.
For client it only works with characteristic that has
WriteAcquired property which relies on
write-without-response Flag.
To release the lock the client shall close the file
descriptor, a HUP is generated in case the device
is disconnected.
Note: the MTU can only be negotiated once and is
symmetric therefore this method may be delayed in
order to have the exchange MTU completed, because of
that the file descriptor is closed during
reconnections as the MTU has to be renegotiated.
Possible options: "device": Object Device (Server only)
"MTU": Exchanged MTU (Server only)
"link": Link type (Server only)
Possible Errors: org.bluez.Error.Failed
org.bluez.Error.NotSupported