Lab
Which Bluetooth module do I actually have?
Every setting in this subject depends on which module you are holding, and that is the thing people are most often wrong about. HM-10 is a name printed on modules that are not HM-10s, and a genuine one wants the opposite line ending to the clone sold as one.
This asks only what you can check in a minute: how many data pins the board has, whether it carries a small button, and what a bare AT does. The first two are physical. The third is behavioural, and it is the one that settles it.
Behaviour beats appearance every time. A module that answers with no line ending has told you it is an HC-06 or a genuine HM-10. One that answers only with Both NL & CR is an HC-05 or a clone. No amount of reading the silkscreen is worth as much as one reply.
If the evidence is thin it says so rather than guessing. A confident wrong answer here sends you to the wrong row of the table and the wrong dropdown, which is the expensive mistake this is trying to prevent.
What this shows
The settings are useless until you know the part, and the part is the thing people are most often wrong about. HM-10 is a name printed on modules that are not HM-10s.
This asks only what a stuck reader can actually check: how many data pins the board has, whether it carries a small button, and what a bare AT does. Pin count and the button are physical; the reply is behavioural, and the reply settles it.
Behaviour beats appearance. A module that answers OK with no line ending has told you it is an HC-06 or a genuine HM-10; one that answers only with Both NL & CR is an HC-05 or a clone. No amount of reading the silkscreen is worth as much as one reply.
It will tell you when the evidence is thin rather than guess, because a confident wrong answer here sends you to the wrong row of the table and the wrong dropdown.
Common questions
- How do I tell a genuine HM-10 from a CC41-A or AT-09?
- By the line ending it accepts. A genuine HM-10 answers a bare AT with no line ending at all and rejects an appended carriage return. The clones want Both NL & CR. They are sold under the same name, so the reply is a better test than the label.
- My module has six pins and a button. What is it?
- That is the HC-05 shape, but the shape is not proof. Confirm it by setting the passthrough sketch's BT_BAUD to 38400, holding the button down while applying power, and setting the dropdown to Both NL & CR with the Serial Monitor left at 9600 — an HC-05 in command mode answers a bare AT with OK and blinks roughly once every two seconds.
- Nothing answers at all, on any setting. What now?
- Silence across every dropdown setting usually means you are not in command mode rather than that the module is faulty. An HC-05 needs the button held while power is applied. An HC-06 and an HM-10 answer only when nothing is connected to them, so disconnect the phone first.
- Does the number of pins tell me anything on its own?
- It narrows it. Six pins with a button is the HC-05 layout; four pins and no button is the HC-06 shape, but BLE modules also come on four-pin boards, so pin count alone cannot separate an HC-06 from an HM-10 or a clone. The bare AT does that.