BTnode rev2_2 Design Data
BTnode rev2_2 Engineering Change Order [pdf]
Block Diagram of rev2_2
Feature Description
Serial programming on UART0 using either an ISP or an STK500 on connector J1. UART0 usually connects to the Bluetooth module. The TX and RX lines are disconnected on programming and reset by the switch U1.
External 60kbitx8 SRAM starting at address 0x1100.
External reset either through switch S1 or pin 5 on connector J1. The default assembly is internally pulled high.
Realtime clock through X2 and 7.3728 MHz system clock through X1.
Four LED's are accessible through outputs PB4-7.
Single power supply through connector J9. The input range of the linear regulator is specified from 3.6 to 16 V DC (I have tried a voltage range from 2.9V up, and it seems to work ok). A three cell battery pack is thus most suitable.
Battery charge indicator on analog input PF2. The value measured depends on the voltage divider R15/R16 and must be smaller than Aref. Vbat_in is calculated to be Vbat_in=Vbat*R16/(R15+R16). The default assembly is R3 = 0 Ohm, R15 = 2.7kOhm and R16 = 10 kOhm with Vbat_in=Vbat*10/12.7 and Aref=Vcc.
The Bluetooth module can optionally have a seperate power supply that can be switched off by output PF2. The second power supply can either be left unpopulated and Vcc be used for the Bluetooth module. For this R11 needs to be populated with an 0 Ohm resistor. The default assembly is that R11 is populated and U7, R9, R10, C12 and C14 are not.
The Bluetooth module has a reset pin connected to output PF1 and hardware enable connected to PF0. This allows for a flexible use of the different power modes on the Bluetooth module.
Current access for measurement of power consumption is available for the CPU (R2), memory (R12) and Bluetooth (R6). The default assembly is a 0 Ohm resistor in each position.
Power Consumption Profile
The following table summarizes the
average power consumption of a BTnode and it's components in various operating
modes. The values given are computed and measured at 3.3V operating voltage.
| Mode | P [mW] Datasheet | P [mW] Operation | |
| BTnode_rev2_2 | |||
| ATmega128l | active | 8*3.3 | |
| ATmega128l | idle | 4*3.3 | |
| ATmega128l | power-down WDT | 0.025*3.3 | |
| ATmega128l | power-down | 0.010*3.3 | |
| SRAM memory | |||
| Bluetooth | disable | ||
| idle | |||
| connected, idle | |||
| full tx or rx |
Datasheets
Atmega
128L
Amic LP62S2048X-70LLT or Amic
A62S6308X-70SI or Cypress
CY62128VLL-70ZAC
BT
ROK 101007
Suyin ROK Module
Carrier
National LP2987
Fairchild 74LCX573
Fairchild NC7WB66
Seiwa SCM-309S
Epson MC-309
Molex Connectors 51021 and 53261
You can order the necessary connectors at Farnell under order numbers 889-477 (2-pin) and 889-490 (6-pin).
Design Data
The top and bottom view of the new boards for BTnode rev2_2.
Schematic
[pdf]
Assembly Top [pdf]
Assembly Bottom [pdf]
Bill of Material [txt]
Netlist [txt]
Placed Components [txt] and the actual assembly data for the default assembly [txt] [xls]
!! Attention Extended Memory Patch !!
If you have read so far and want to build your own BTnodes, drop me a line and i will gladly provide you with the PCB design data. mailto: j.beutel@ieee.org
last
edited