This document describes the design and implementation of a USB controlled function generator using a XR-2206 analog signal generator chip and a Silicon Labs C8051F340 microcontroller. Key features include programmable signal generation over a wide frequency range that can be controlled from a PC. The design provides advantages over a completely digital approach such as faster analog signal generation.

1. USB Controlled Function Generator Design and Implementation by Kent Schonert (Kent.Schonert@sbcglobal.net)

9. Wave Form Switching Switch Replaced with Resistor (no distortion) Switch in place to alternate waveform on demand (minimal distortion)

15. USB Data Exchange PC Host Read Request In USB Buffer Out Data PC Host In USB Buffer Out Data Data to Target Device Data From Target Device Packet type/# Information In_Packet[0] Limit(s) Hit In_Packet[1] A/D Conversion In_Packet[2] Port1 Status In_Packet[3] Amp. PCA Value In_Packet[4] Freq. PCA Value Out_Packet[0] Amp. Hi Byte Out_Packet[1] Amp. Lo Byte Out_Packet[2] Freq. Hi Byte Out_Packet[3] Freq. Lo Byte Out_Packet[4] Freq. Multiplier Out_Packet[5] Out_Packet[6] Waveform Select

16. Software on Host

17. Firmware on `F340 Target

20. Cost Analysis Initial Prototype Part Qty Price each C8051F340 (Dev Kit) 1 $100 $100 XR-2206CP 1 $3.29 $3.29 CD4016 (Quad Switch) 1 $0.29 $0.29 LM741 (op-amp) 3 $1.10 $3.30 DM7406 (OC inverter) 1 $0.40 $0.40 Capacitors 5 $0.10 $0.50 Resistors <20 low $1.00 Bread Board 1 $3.50 $3.50 Power Supply 1 $15.00 $15.00 Total $127 Surface Mount Technology C8051F340 (SMT Unit) 1 $9.41 $9.41 XR-2206D 1 $10.00 $10.00 Power Supply 1 $15.00 $15.00 Capacitors 11 $0.10 $1.10 Resistors <20 low $1.00 Solid State Relay (2ohm) 1 $5.33 $5.33 PS7113L-2A-A (quad) LMV934MA-ND 1 $1.66 $1.66 Op amp (quad) sp0503baht 1 $0.40 $0.40 Diode Pack PCB Board 1 $4.00 $4.00 Misc Pins/Jumpers x x $4.00 AU-Y1007-R 1 $1.16 $1.16 USB B to PCB Price $53.06 Price (low) $28.65

22. Questions?

23. Instruction Function Mnemonic Clk Cycles Push double pointer (Hi/Lo) PUSH direct (DPH/DPL) 4 Push A PUSH A 2 increment counter INC direct 2 move counter to A Mov A, direct 2 Subtract max ptr size from counter SUBB A, #data 2 Jump to reset pointer if at max JZ 2 Move offset to Double Pointer (Hi) MOV DPH, direct 2 Move offset to Double Pointer (Lo) MOV DPL, direct 2 Fetch Hi data from code memory MOVC A, @A+DTPR 2 Put Hi data into DAC register MOV direct, A 2 Increment A INC A 1 Fetch Lo byte from code memory MOVC A, @A+DTPR 2 Put Lo byte into DAC register MOV direct, A 2 POP A POP A 2 POP double pointer (Hi/Lo) POP direct (DHP/DPL) 4 Return from interrupt RETI 6 Total: 39 Tolal/48Mhz : 8.125E-07s 50%*1/(20*Update time): 3.08E+04Hz

24. Full Schematic XR-2206