Products > Test Equipment
SainSmart DDS120 & DDS140 USB Oscilloscope
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doctormord:
@merbanan,

You have my permission.

Just link back to "360customs.de". :)

Regards.

merbanan:
Ok, I have now added:

http://sigrok.org/wiki/SainSmart_DDS120

For the record here is the Hantek 6022BL sigrok driver:

http://sigrok.org/gitweb/?p=libsigrok.git;a=tree;f=src/hardware/hantek-6xxx;hb=f2a66a8ee669df5afa1b7bdade6e25ac0857fe4b

And then the more interesting part the firmware:

http://sigrok.org/gitweb/?p=sigrok-firmware-fx2lafw.git;a=commitdiff;h=189db3d41e4c3d8a4aec5ec605c03df75577d531



So from reading the thread I have come to the conclusion that the Hantek and SainSmart are fairly similar but there are vital differences that will hinder the use of the Hantek firmware directly.

To start with how does the gain stage work ? What pins control that ?
doctormord:
If i remember correctly and from the pictures:

PE3 = Channel A AC/DC via Photomos; enabled Photomos bridges AC input cap
PE0 = Channel B AC/DC via Photomos; enabled Photomos bridges AC input cap

PC1= enables Channel A compensation Network
PE1= enables Channel B compensation Network

I'm not sure if it is always enabled when doing AC coupling.

PC2 + PC3 = selects Channel B gain
PC4 + PC5 = selects Channel B gain

PB7-PB0 = Channel A 8bit input D7(MSB)-D0:
PD7-PD0 = Channel B 8bit input D7(MSB)-D0:




merbanan:

--- Quote from: doctormord on March 15, 2016, 10:10:41 pm ---PC1= enables Channel A compensation Network
PE1= enables Channel B compensation Network

I'm not sure if it is always enabled when doing AC coupling.

PC2 + PC3 = selects Channel B gain
PC4 + PC5 = selects Channel B gain


--- End quote ---

What is a compensation network (when would the firmware enable it) and can you clarify Channel B gain (it's there 2 times)?

What bits correlate to what gain ?
doctormord:
The compensation network is right beside the white BNCs. I'll have to overthink it.

Edit: Compensation is always active, see schematic.

The gain stage were discussed here:

https://www.eevblog.com/forum/testgear/sainsmart-dds120-usb-oscilloscope-%28buudai-bm102%29/msg535341/#msg535341

It's a 2 stage approach. -6dB and -20dB on the first stage. The second stage is then doing the gain by 3 different resistor values switched into the feedback loop.

So there is:

First stage (Attentuator):
PC1: 0 = -6dB, 1 = -20dB
PE1: 0 = -6dB; 1 = -20dB


--- Quote ---and can you clarify Channel B gain (it's there 2 times)?
--- End quote ---

Sorry, typo, it is:

PC2 + PC3 = selects Channel A gain
PC4 + PC5 = selects Channel B gain
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