last updated: March 2, 2008
With this link, information that is sent to the robot's display is also sent to a nearby laptop. From the laptop, commands can be sent to the robot. The two units are almost identical. The only difference is how they're powered. On the PC side, power comes from 2 AA batteries and supplies the Laipac module, PIC and level shifter. On the robot side, 5V comes from the robot, passes through the RS232 cable, to the 3V regulator and the Laipac module and PIC
I'll be getting some boards made soon (aiming for summer of 2008). They'll be about 0.8" X 1.2" and should cost somewhere from $3 to $5 each. Let me know if you're interested getting 1 or more.
Outdoors:
In a parking lot with no obsticles, I had no problems at 100m. If I point the units at each other and make sure I'm not standing in the way, they could be up to 200m from each other.Indoors:
Can't get them to fail while they're in the house. I even tried putting one unit in a metal filing cabinet!
In versions 1 and 3, only the first byte is usedbyte 0 - user data
byte 1 - user data (used only if there's data left in the UART rx buffer)
byte 2 - user data (used only if there's data left in the UART rx buffer)
byte 3 - left nibble: payload type, right nibble: # of user bytes used
byte 4 - sequence # to be acknowleged
byte 5 - sequence # being acknowleged
(same code in both units)
written in C for the CCS compiler
| version | UART buffers | speed | packet loss | link indicator | range | bytes sent per packet | lost packet management |
| 1 | none | 1Mb/s | 10% | no | much less than version 8 | 1 | none |
| 3 | rx | 1Mb/s | 10% | no | much less than version 8 | 1 | none |
| 8 | rx & tx | 250kb/s | 0% | yes | 100m-200m outside, no obsticles |
1 to 3 | re-sent when ack not received |
This unit plugs into the serial port of a PC
This unit connects to the robots main controller
Parts list
| Laipac TRF-2.4G 2.4GHz RF module (known as TXRX24G at Quality Kits)
This module is made by Wenshing in Taiwan. It's based on the nRF2401A RF transceiver chip from Nordic Semicondutor. Laipac imports them and covers the manufacturers name with a black blob. |
Quality Kits (Kingston) |
$13 |
|
 breakout boardI didn't use these because I didn't know about them at the time. They would have made wiring much easier. |
Spark Fun(By the way, their website is worth spending some time at) | $1 US | |
| PIC 16F628 (I'll upgrade to a 16F688 soon) | Digikey | ||
 RS232 converter (DCE version) SKU#30000 |
HVW Tech | $12 | |
| 3V regulator * | Digikey | ||
| 4MHz resonator | Digikey, Active | ||
| 22uF capacitor * | Digikey, Active | ||
| 2.2uF capacitor * | Digikey, Active | ||
| PC board | ADD Electronics | 85¢ | |
| .1uF surface mount capacitor - 0805 size | Digikey | ||
| 2 - 2 pin KK headers | Digikey, Active | ||
| 4 pin KK header | Digikey, Active |
* For voltage regulation. Not needed if powered by 2 AA batteries
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