Using an INHAOS LC-1000 with the Picaxe

Goeytex

Senior Member
#1
I received several INHAOS LC-1000 RF Transceiver modules a while back and have finally gotten around to testing them with a Picaxe. They work amazingly well for short range RF comms.

The main challenge for the hobyist is to get wires/ connectors on to the LC-1000 module. The pad spacing is only 1.27mm so soldering leads or a connector will require a fine tip soldering iron, solder flux, and a big magnifier. I used 28ga stranded hookup wire. My units were supplied with a 1.27mm spaced male header that was not installed. However a search for a 1.27mm female connector/header was fruitless. INHAOS should consider the option of the installing the header on the module and supplying a connector with flying leads. Another option might be a breakout board with 2.54mm pin spacing.

The LC-1000 operates in the 2.4 Ghz ISM band. It transparantly uses frequency hopping / clear channel assessment across the band so crowded channels and channel selection are not something the user needs to be concerned with. It is all done seamlessly via the RFIC and MCU.

Each module has a unique ID or address that is laser etched on the body of the RF shield. A sticker on the shield indicates the factory programmed link address, which is the address of the other module to communicate with. At power on the both of these addresses are loaded from the modules EEPROM and the module does handshake.to establish an RF link with the module at the programmed link address. Once linked, serial data sent from one module is received by the other module and is then sent out receiving module's TX pin.

LC-1000 can be programmed to change several parameters

1. Local_Address (64 bit address)
2. Link_Address (64 bit address)
3. Serial Baud Rate (2400 to 57600)
4. Sleep_time (0 to 65535 seconds)
5. Working Mode (Sleep or normal)

All of these settings can be saved to the module's EEPROM except the Local Address. This is not noted in the Datasheet. The local address can be changed within a program if necessary, but that change will be lost either after a "hard reset" or soft reset LC-1000 module. It will then revert back to the UID etched onto the module.

The Datasheet also shows a Carrier setting which implies that the RF channel can be changed by sending command $EF to the module. Don't use this command. This command is ONLY for engineering use and FCC testing with a spectrum analyzer. IF you use this command the module will stop working until the power is cycled off / on.

The LC-1000 uses automatic frequency hopping ( also not clearly stated) so manually changing channels is not necessary or supported. The RF channel is automatically determined by the LC-1000.

There is no configuration utility provided specifically for the LC-1000. However, configuration can be done through a terminal program or with Picaxe Basic Code. I have included examples in the Demo Program that gives shows how to do this.

Serial communication to and from the Lc-1000 is always non-inverted and 8,N,1. The baud is determined by the baud setting in the LC-1000 EEPROM or by the last baud command. Once the baud rate is changed, whether or not the change is save to EEPROM the module will only communicate at the new baud rate. The default power up baud rate is 9600. However if it has been changed and the change saved to LC-1000 EEPROM, it will power up at the changed rate. The baud rate can always be reset to 9600 by powering down the LC-1000 and holding the config pin low for > 200ms while powering the module back up.

There are 12 valid commands for changing & reading the configuration settings. To set or read a setting the config pin must be taken low and then a 13 byte packet sent to the module's RX pin.

The packet is in the format of :
Checksum, save_byte, command, num_bytes, val_1,val_2,val_3,val_4,val_5,val_7,val_7,$0D,$0A)

The checksum can be computed in Picaxe BASIC as:
Code:
Checksum  = save + cmd + numbytes + val_1 + val_2 + val_3 +val_4  + val_5  +val_6 +val_7 + 13 + 10
Checksum   = NOT Checksum
The save byte determines if the register setting value(s) is saved to the LC-1000 EPROM or not. The save byte is ignored with CMD $FO. Valid commands are $CE,$CF, $F0 through $F5 and $D0 through $D5. Do not use $EF listed in the datasheet on page 17. $EF is for testing/validation only and using it will cause the LC-1000 to stop working properly until reset.

Read Commands:

$CE Read Device Type 7 bytes
$CF Read Firmware Ver 2 bytes

$D0 Read Local Addresss 4 bytes
$D1 Read Link Address 4 bytes
$D2 Read Baud Rate 2 bytes
$D3 Read Sleep Time 4 bytes
$D4 Read Work Mode 1 byte
$D5 Read RF Power Level 1 byte

Write Commands:
$F0 Set Local Address ( save byte is ignored)
$F1 Set Link Address
$F2 Set Baud Rate
$F3 Set Sleep Time
$F4 Set Work Mode
$F5 Set RF Power Level

After receiving a valid command packet with the correct checksum, the LC-1000 will reply with it's own 13 byte reply packet. The packet will be in the same format as the one sent. If the packet received is valid, the LC-1000 will return 13 bytes, one of which is the command byte. If there is an error, the cmd byte will be returned as either $E1 (invalid command) ,$E2 (bad checksum) ,or $E3 ( Invalid Data). The demo code does not check the reply for errors. This can be added if needed.

The settings that will most likely need to be changed are link_address and baud_rate. Examples are included in the Demo Program

Attached is a Demo Program and a schematic. The demo program uses a Picaxe 20X2 for wireless chat between 2 PC's. The Picaxes were used to add
add some bells and whistles to allow use of the Picaxe Terminal and to allow programming and chatting without having to add a second serial port or USB TTL module.

The schematic includes a 10K thermistor that connects to an ADC input. A loop can be added to the code to wirelessly transmit the ADC value (Temperature) to a PC or even to a stand alone unit.

This demo program should give a good idea how to use the LC-1000 and should offer a foundation for more complex applications.

I used Picaxe 20X2's for interfacing to the LC-1000. The main reason being the capability of hardware background receive which is fast and allows for dynamic packet lengths and a circular receive buffer if needed. However the LC-1000 will work fine with M2 Picaxe chips, but the code and connections will need to be modified.

Enjoy
 

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Pongo

Senior Member
#2
Hmmm, a true serial in, serial out, bidirectional wireless link for only $10, very interesting. Thanks for posting the info :)

Did you explore the limits of the range at all?
 

tony_g

Senior Member
#3
i have been so busy with other things i forgot i had theses to play with some more for a distant future project that would benefit from them and their simplicty, one thing i will add, changing the capacitor from the default SEL1 to SEL2 to use an external antenna was an amusing task, i normally use 0805 sized caps and resistors so 0402 did invoke a few curse words but ended in succes, i still have to get another antenna for the other module and then to see how the range improves, i dont need ridiculous long range but i would like to have a good workable distance between the two if it comes down to it, but overall im impressed with my short brief play i had with it with a couple of 08M2's

thanks for the write up and demo code goeytex :D and have a merry xmas.

tony
 

lbenson

Senior Member
#4
Do these modules just do one-to-one links or can there be many-to-one configurations. For instance, can A, B, and C link up (one after the other, not simultaneously) with D?

To ask another way, can "D" be listening for a linkup, and then make the link when A, B, or C initiates it, and then drop the link and go back to listening mode?
 

Goeytex

Senior Member
#5
That should be possible by periodically setting / changing the "link address on Module D" and with use of the signal on the LC-1000 "lnked Pin" on the other respective modules.
 

lbenson

Senior Member
#6
Ok, thanks. I thought that should be the case--too inflexible otherwise.

Are you saying that Module D has to know which initiating module will try to link with it? So that there would have to be a kind of round robin, where D listens for A for, say, a second, then for B for a second, then for C? Or can D just be listening, and the first to initiate will make the link?
 
#7
Hi
@goeytex

Regarding your first post about 1.27mm headers. I did a search here in the uk and found several companies
offering several variants. CPCfarnell, Harwin etc.. did you manage to source any?
regards john
 

Goeytex

Senior Member
#8
Ok, thanks. I thought that should be the case--too inflexible otherwise.

Are you saying that Module D has to know which initiating module will try to link with it?
Yes. D only listens for data from the module at the programmed link address.

So that there would have to be a kind of round robin, where D listens for A for, say, a second, then for B for a second, then for C?
Correct.

Start D programmed with a bogus link address. The link pin will be high indicating no RF link.

Set link address to A.
The link pin will then go low on both A & D. ( low = linked)
Data can be transferred.

Set Link Address to B.
Link pin on A will go high ( not Linked). Link pin on D will pulse high for a few ms then go low. Link pin on B will go low.
D & B are linked. Data can be transferred.

A nice thing about the LC-1000 is (unlike most RF modules with "Firmware" such as Hope & Dorji) that changing the Module's setting parameters does not automatically write to EEPROM (unless you tell it to). So constantly repeated parameter changes such as above will not "wear out" the embedded MCU's EEPROM in a few weeks.
 

lbenson

Senior Member
#9
This may not be the best place to ask, but what, gooeytex (or others), do you currently think is the best, not too expensive, transceiver for picaxe use (15-20 meter range). Serial control rather than spi would be a bonus.
 
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