It seems a friend of mine lurks on this forum, read this thread and came around last night to lend me a couple of spare HC-11s, that I can replace when mine arrive from China.
So, I thought I'd start by doing some basics and learning how to programme them. First off, the better datasheet (this one:
http://www.elecrow.com/download/HC-11.pdf ) isn't 100% clear, so I thought some really basic instructions may help.
Equipment used:
Standard USB FTDI module connected to PC, with these connections
FTDI HC-11
+5V +5V
GND GND
Tx Rx
Rx Tx
CON on the HC-11 to ground for AT mode, open circuit for normal mode
Terminal emulator used was Termite on Windows PC, with the following initial settings (important, as other settings caused some problems)
Baud rate 9600, 8 bits, no parity, no stop bit, no flow control, no forward
Transmitted text – nothing (so no added CR etc)
Echo on (just for convenience, could be off)
No word wrap, no function keys, no hex view, no log file, no status LEDS
Options settings seem unimportant, but I only had close on cancel selected.
To programme the HC-11 then power it on with the CON connection connected to 0V and leave it connected to 0V.
Follow the programme instructions in the data sheet when in AT mode. For example, here is a screen grab from Termite of me checking the setting of the unit (using the AT+RX command) and then setting the frequency channel to 15 (015) and the address to 150 (0 to 255 is possible)
First, a screen grab showing the bare module as received and its settings:
AT+RXU1
B9600
C001
A000
P8
The blue is the echoed command sent, the green is the data received from the HC-11
As you can see, the default settings are Baud rate = 9600, Channel = 001, Address = 000 and transmit power level = 8 (which is +10 dBm - see datasheet for other power settings).
Next, I will send commands to the HC-11, in AT mode (CON held low) to programme new settings:
AT+C015OK-C015
AT+A150OK-A150
AT+P6OK-P6
These settings have changed the channel to 15, the Address to 150 and the transmit power level to 5dBM (level P6).
To check that these settings have been saved, the HC-11 is unplugged and then plugged back in, so the setting should now be stored in EEPROM.
To check this, the HC-11 is reconnected, with the CON line held low, and the command AT+RX is used to read out the module saved setting:
AT+RXU1
B9600
C015
A150
P6
As before, the blue text is the transmitted command, the green text is the response from the HC-11. As can be seen, the previously programmed settings have been retained during power down and the module is still set to work at 9600 baud, on Channel 15, with the address 150 and a transmit power level of 5 dBm (P6).
The default settings can be recovered at any time by entering AT command mode and sending AT+RESET, which will restore the unit to the original settings. Be aware that doing this will set the baud rate back to 9600, so if that has been changed then you will need to reset your terminal emulator to the new baud rate to be able to communicate with the HC-11 post-reset.
Up to 20 frequency channels and 255 address channels can be set, giving lots of space for multiple links working in the same area
Please read this in conjunction with the attached datasheet for more information.
I still have more playing to do, but I can see these being very useful for use with a Picaxe. For example, there are three digital input/outputs when the modules are programmed with the transmitting module setting AT+FCMF and the receiving module setting AT+FCSF Up to 20 frequency channels and 255 address channels can be set, giving lots of space for multiple links working in the same area. This measn you could, for example, have a simple set of three push buttons (or a matrix of up to 8 push buttons) connected directly to the transmitting HC-11. The receiving HC-11 would then present a Picaxe with three lines (5V compatible) that would mimic the state of the remote push buttons.
The units can also be used as a stand alone full of half duplex UART link, with up to 255 addresses and 20 different frequency channels, allowing normal comms links between devices, or broadcasting (to all units on the same channel and address) if required.
I have to say, from the little bit of playing around I've done this morning I have to say these look to be very easy to use and versatile, and they are cheap if you buy them in significant quantities, I ordered 10 from China for around £30 including postage, so around £3 each, which seems very good value, and they include small helical antenna.
I'll report back more once I've established how well they work "in the wild".