' ***** Ultrasonic Goertzel Demo (output + input + display) ' ' The P2 Goertzel circuit measures up to four ADC input signals for magnitude and phase ' correlation of four internal reference signals, which can also be output to form closed- ' looped systems. ' ' In this demo, the Goertzel circuit outputs a reference sine pattern to two DAC pins ' which differentially drive a 40 kHz ultrasonic transducer. Another identical transducer ' is connected between GND and an ADC pin, so that its ADC bitstream can be used as input ' to the correlator. On each clock cycle, the correlator multiplies the ADC bit (+1 or -1) ' by the current reference sine and cosine values, accumulating the products into separate ' sine and cosine accumulators. The accumulators can be periodically sampled and converted ' from cartesian to polar form, in order to get the magnitude and phase of the incoming ' signal(s) relative to the internal reference sine and cosine signals. The Goertzel ' measurement is done over 1 to 65,534 complete waveform cycles. The more cycles that are ' measured, the more precise the measurement. ' ' On every clock cycle the Goertzel circuit effectively does this in sequence: ' ' t := LUT[nco[30:22]] (the LUT can be partitioned in 1/2's, 1/4's, etc) ' nco += xfrq (set by SETXFRQ instruction) ' cog_dac_3 := t.byte[3] ^ $80 (cog DAC channel 3 playable on pins %xxxx_11) ' cog_dac_2 := t.byte[2] ^ $80 (cog DAC channel 2 playable on pins %xxxx_10) ' cog_dac_1 := t.byte[1] ^ $80 (cog DAC channel 1 playable on pins %xxxx_01) ' cog_dac_0 := t.byte[0] ^ $80 (cog DAC channel 0 playable on pins %xxxx_00) ' sin := t.byte[3] sign-extended ' cos := t.byte[2] sign-extended ' m := ADC_bit ? 1 : -1 ' sin_accumulator += sin * m (32-bit sin accumulator) ' cos_accumulator += cos * m (32-bit cos accumulator) ' ' After each XCONT, GETXACC can read and clear the accumulators in one clock cycle: ' ' capture sin_accumulator for conveyance to GETXACC's D ' capture cos_accumulator for conveyance to next instruction's S ' sin_accumulator := sin * m (clear to current sin * m) ' cos_accumulator := cos * m (clear to current cos * m) ' ' The Goertzel circuit may also be used to simply detect magnitude of a frequency within a ' noisy signal. In that case, no reference outputs would be needed, because there is no ' feedback loop. ' ' CON _clkfreq = 200_000_000 VAR table[512] 'lut data, 512 * 4 bytes - read once at start dacpins '[0] dac pins to drive +/- sine output - read once at start adcpin '[1] adc pin to sense return signal - read once at start adcmag '[2] adc mag 0..4 = 1x,3x,10x,31x,100x - read once at start frequency '[3] output frequency - read on every measurement cycles '[4] number of cycles per measurement - read on every measurement magnitude '[5] measured magnitude (32-bit) - written on every measurement phase '[6] measured phase (32-bit) - written on every measurement done '[7] done flag = 1 - written on every measurement PUB go() | i, cos, sin, t 'write sin/cos bytes into lut data for Goertzel use debug(`scope p title 'LUT data' size 512 255 samples 512 rate 512) debug(`p 'cos' -127 127 255 0) debug(`p 'sin' -127 127 255 0) repeat i from 0 to 511 cos,sin := polxy(127, i << -9) t.byte[3] := sin 'byte3 is used for Goertzel sine t.byte[2] := cos 'byte2 is used for Goertzel cosine t.byte[1] := 0 'byte1 is not needed for this demo t.byte[0] := sin 'byte0 is used for +/- sine output table[i] := t debug(`p `(cos,sin)) 'set operating parameters dacpins := 0 addpins 1 'differential DAC outputs on P0 and P1 connect to one 40 kHz transducer adcpin := 8 'ADC input on P8 and GND connect to the other 40 kHz transducer adcmag := 4 'full 100x magnification on ADC frequency := 40_000 '40 kHz output/input cycles := 400 '40 kHz / 400 cycles = 100 measurements per second 'start Goertzel program in another cog coginit(newcog, @goertzel, @table) 'show each measurement as it comes in debug(`scope_xy s pos 0 340 'Goertzel' samples 1 dotsize 20 range 10_000_000 polar logscale) repeat repeat until done done~ debug(`s `(magnitude, phase)) DAT org ' Goertzel program that runs in cog goertzel setq2 #$200-1 'load lut from table rdlong 0,ptra++ ' configure dac and adc pins setq #3-1 'read pin data rdlong .dacpins,ptra++ mov .x,.adcpin 'set dds d operand and .x,#%111100 shl .x,#19-2 or .dds_d,.x mov .x,.adcpin 'set dds s operand and .x,#%000011 decod .dds_s,.x shl .dds_s,#12 fle .adcmag,#4 'enable adc pin shl .adcmag,#15 add .adcmode,.adcmag wrpin .adcmode,.adcpin cogid .x 'enable dac pins setnib .dacmode,.x,#2 wrpin .dacmode,.dacpins drvl .dacpins mov .done,#1 'set done flag ' get Goertzel frequency and cycles, start new measurement, output prior results, loop .loop setq #2-1 'read input data rdlong .frequency,ptra++ rdlong .x,#@clkfreq 'compute NCO frequency shl .x,#1 qfrac .frequency,.x getqx .y setword .dds_d,.cycles,#0 'set cycles setq .y 'issue Goertzel command with updated frequency xcont .dds_d,.dds_s getxacc .x 'get prior Goertzel reading, cosine first mov .y,0-0 '..then sine qvector .x,.y 'convert (x,y) to (magnitude,phase) getqx .magnitude 'get magnitude getqy .phase 'get phase setq #3-1 'write output data wrlong .magnitude,ptra++ sub ptra,#5*4 'point ptra back to .frequency jmp #.loop 'loop for next measurement 'Data .adcmode long p_adc_1x 'ADC mode .dacmode long p_dac_124r_3v + p_channel 'DAC mode .dds_d long x_dds_goertzel_sinc1 + x_dacs_0n0_0n0 'streamer mode .dds_s res 1 'workspace .x res 1 .y res 1 .dacpins res 1 'read once at start .adcpin res 1 .adcmag res 1 .frequency res 1 'read on every measurement .cycles res 1 .magnitude res 1 'written on every measurement .phase res 1 .done res 1