Servo - October 2008

application code snippet:

for(i=0;i<tx_end;++i)  //load the transmit packet array
 packet_tx[i] = i+2;

err_led = OFF;
if(rc = set_tx_interval(0x28))
 err_led = ON;
if(rc = set_tx_rx_mode(tr_xmit))
 err_led = ON;
if(rc = set_device_id(0x11, 0x22, 0x33, id_xmit))
 err_led = ON;
if(rc = set_network_id(0x00,0x00,0x00))
 err_led = ON;
if(rc = set_ad_settings(0x00,0x00,0x00,0x00))
 err_led = ON;
if(rc = set_network_mode(p_to_p))
 err_led = ON;
if(rc = set_tx_pwr_lvl(dbm_plus5))
 err_led = ON;
if(rc = send_data_buffer(no_xmit))
 err_led = ON;

SCREENSHOT3.

The Hard Work is Done

Before running the API transmit application, I commanded the laptop EmbedRF to search for the first transmitter it could hear. Kicking off the API transmit application resulted in the EmbedRF DesktopPRO “hearing” the PIC’s EmbedRF and establishing a session with it. The results of the communications session can be picked out of the EmbedRF DesktopPRO window you see in Screenshot 3.

According to the API transmit application code snippet, the PIC’s EmbedRF transmit device ID is 0x112233 or 1,122,867 decimal. The PIC’s transmit device ID is verified in Screenshot 3. The 10-byte data packet transmitted by the PIC’s EmbedRF begins with 2 and ends with 11. This is also backed up by the Raw Data Received view in Screenshot 3. We disabled all of the EmbedRF’s A-to-D inputs, so you can ignore the Analog Data Received numbers as they are just the hex values of the data we entered into the data packet. For instance, A/D 0 says it sees 515 counts. That’s because it’s calculating 0x0203 (515 decimal) as an A-to-D reading. The same goes for A/D 1, which is a result of 0x0405 or 1029 decimal.

Take a look at the EmbedRF datasheet and you’ll see that there are many more commands than we have discussed here. The good news is that every EmbedRF command has a corresponding API function call; I’ve tested all of them. So, all you have to do is put them together to form your own unique EmbedRF application. To ease your learning curve, I went to great lengths to make sure that the API call arguments closely matched the EmbedRF command descriptions in the EmbedRF datasheet. Integrating the EmbedRF hardware is a no-brainer and with the availability of our home-brewed EmbedRF API, bringing an EmbedRF network online is a walk in the park. I’m sure that you won’t have any trouble coming up with an application for the EmbedRF data radios. See you next time! SV

Sources Saelig — www.saelig.com EmbedRF; EmbedRF Development Kit

HI-TECH Software — www.htsoft.com HI-TECH PICC- 18 PRO

Microchip — www.microchip.com PIC18LF2620; MPLAB IDE; MPLAB REAL ICE

Make your product wireless - quickly, conveniently, and affordably. EmbedRF is a rapidly-deployed, turn-key, networkable wireless solution for low data rate, ultra low-power analog or digital applications. Avoid lengthy RF development time by using EmbedRF short-range low-power wireless modules in your product design. Notable features: RSSI output – ideal for finding nearest module or position tracking; current levels are CR2032 coin-cell friendly (average current to <12uA Tx/Rx); >0.25s periodicity; unique IDs avoids cross-talk; < 6mS link latency; buffered receive data allows for other system priorities.