[Coco] USB (RS-232?) O-scope

[Gene Heskett]

On Thursday 25 February 2010, Frank Swygert wrote:
>Saw this at
>http://www.instructables.com/id/DPScope-Build-Your-Own-USBPC-Based-Oscillos
>cope/ and thought some of you might be interested. Looks like a good way to
> get a cheap o-scope, but I'm not sure if the specs are good enough for
> working with a CoCo. The only drawback is the software is Windows based,
> but maybe one of you Linux guys can fix that -- or it might run under
> WINE, or could be run in a virtual PC window....  It uses a USB
>interface, but it should be convertible to RS-232. Uses a PIC
>microcontroller. If RS-232 is doable I wonder if software could be
>written for a CoCo? Since the PIC is doing most of  the work the
>computer should just be a display device, but the CoCo screen or serial
>might not be capable of displaying fast enough -- then someone has to
>write the software too...
>
>*Input:
>*
>Number of channels: 2
>Analog bandwidth: > 1.3 MHz

Way too slow, you need at least 10x the observed waveforms bandwidth in the 
device to get anywhere near a display you can believe in.  That would only be 
usable for audio since the top signal in the coco is in the 28mhz range.  My 
own Hitachi dual trace scope, while usable to 200mhz but way out of 
calibration as its rated at 100Mhz, is just adequate to display the output of 
the gime or the address and data lines.

>Input impedance: 1 MOhm || 15 pF
>Probe connection: BNC
>Usable probe types: Standard 1:1, 1:10, 1:20 probes
>
>*Vertical (voltage) scale:
>*
>Vertical sensitivity (20 divisions):
>- 5 mV/div to 1 V/div (1:1 probe)
>- 50 mV/div to 10 V/div (1:10 probe)
>- 100 mV/div to 20 V/div (1:20 probe)
>
>Vertical offset: 0 - 20 divisions
>
>Maximum voltage range
>-12V ... 20V (1:1 probe)
>-120V ... +200V (1:10 probe)
>-240V ... +400V (1:20 probe)
>
>Probe compensation: yes (2 kHz calibration output)
>
>Offset adjustment: yes
>
>*Horizontal (time) scale:
>*
>Max. sample rate (single shot): 1 MSample/sec
>Max. sample rate (repetitive signals): 20 MSamples/sec
>
>Timebase settings (scope mode): 0.5 usec/div ... 1 sec/div
>Timebase settings (datalogger/roll mode): 0.5 sec/div ... 1 hr/div
>
>*Trigger:
>*
>Trigger source: CH1, CH2, auto (free run)
>Trigger polarity: rising edge, falling edge
>Trigger noise reject: yes (selectable)
>Pre-trigger capability (i.e. can show what happened
>before the trigger event): 0 - 20 divisions
>Post-trigger delay (delayed scan, to look at the
>signal long after the trigger event but with high
>resolution): 0 - 200 divisions
>
>*Acquisition:
>*
>Record length (normal mode): 200 points/channel
>Record length (FFT mode): 400 points/channel
>Max. screen refresh rate: up to 40+ frames/sec
>Datalogger mode (roll mode): yes (data can be logged to file in real time)
>
>*Display:* *
>*
>Real-time FFT: yes
>FFT filters: Rectangular, Hanning, Hamming, Blackman
>Averaging: yes (2 / 5 / 10 / 20 / 50 / 100)
>X-Y mode: yes
>Display styles (can be combined): Points, Vectors (Lines), Infinite
>Persistence
>
>Time and level measurements: yes (using cursors)
>
>*Save & Restore:
>*
>Waveform export (e.g. to Excel):yes (CSV format)
>
>Save/restore of scope setups: yes
>
>*PC Software:
>*
>PC connection: USB, 500 kbaud
>PC software: Windows 2000, XP (SP3), Vista, 7
>Minimum screen size: 800 x 600 pixel
>
>*Mechanical construction:
>*
>Power supply: through USB (5V / 250mA)
>(external supply 7.5 - 9V / 300mA optional)
>


-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
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