DLO-138 OScope

What are you developing?
mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Sat Aug 26, 2017 1:59 am

I test now a new version with "BluePill" and instead of the touch-input a second rotary encoder.

I have mounted a parallel resistance from about 1.8 kOhm between 3.3V and PA12, so I can program the Pill via USB with Arduino IDE 1.8.4. The memory is set to 128k (in the STMFlashloader). I have also shorted the 100 kOhm resitance on Boot1, so I can use PB2 (perhaps for a 8-bit display).
I take the encoders from madias (multi-encoder with timer1).
I use this pins:
A0 Analog Input 1
B0 Analog Input 2
B10 TFT_DC
A7 TFT_MOSI
(A6 TFT_MISO)
A5 TFT_SCK
A4 TFT_CS
3.3V TFT_RST
B3 Encoder_0
B4 Encoder_0
B12 Encoder_1
B13 Encoder_1
B6 TEST_WAVE

The program runs stable, the encoders (EC11, KY-040) have no problems with bouncing.

Now I have to build the input amplifiers (with MC6S22 ?)

Good information (inl. schematic) for preamps is on this page :

damusician.com/dpscope/overview.html


mausi_mick

mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Sat Aug 26, 2017 2:00 am


User avatar
rexnanet
Posts: 203
Joined: Wed Mar 16, 2016 10:34 am

Re: DLO-138 OScope

Post by rexnanet » Mon Aug 28, 2017 3:45 pm

Nice! I've tried to setup an input amplifier using 2x MCP6S92 to get up to 1024 gain settings but I got some DC offset on the first stage that got amplified on the second stage and showed up on the output. I was inputting a 0 to 3.3V square wave then divided by 10 (or more... don't remember...) with 2 resistors, that might create a small offset...maybe...
I haven't debugged it yet... I don't have an oscilloscope to check that out so it might be working ok but that's what I saw on the screen.

I have also looked to the input stage of the nano DSO203. Seems good and might be upgraded with better opamps to get more BW:
https://goo.gl/images/58mzQy

P.S. Does anyone have a version of the DSO150 code? That one might be interesting also... I'm tempted to buy one of these...
P.S.2 Can you share the code?

mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Wed Aug 30, 2017 2:32 am

I want to make the Offset with a DAC , I tested it with MCP4812/22 (SPI-Interface), but had no success.
I think the difficulties come with the TFT-Lib. Therefore I tried it with an I2C DAC (MCP4725) with success, but In need
Pins PB6 PB7, so I had to eliminate the TEST_WAVE on PB& :cry: :cry: :cry:

I think I take the MCP6S22 for amplifying (similar DP-Scope V1.3)

I modified the menu for service with the second encoder, on bottom left I start with the timeBase, than Vgain1, Vgain2 (from MCPS622), Offset1, Offset2 (from 2 MCP4725, in work, not finished), trigType and trigEdge ...

The handling with the encoders from madias is normaly quick exapt for sampling (with timeBase >2ms).

mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Sun Sep 03, 2017 11:08 am

Rexanet,

I think , the preamp in DSO203 is very complex , is much work.
Perhaps It's easier to take a LTC6912-1 (2 channel ,gain: 0,1,2,5,10,20,100) or an LTC6912-2 with gain 01,2,4,8,16,32,64),
and you need only a input stage(for dividing and protection with clamp-diodes) and a voltage spltter to 2x3.3V or 2x5V.
The LTC has also 3 wire SPI.

User avatar
rexnanet
Posts: 203
Joined: Wed Mar 16, 2016 10:34 am

Re: DLO-138 OScope

Post by rexnanet » Mon Sep 04, 2017 8:16 am

mausi_mick wrote:
Sun Sep 03, 2017 11:08 am
Rexanet,

I think , the preamp in DSO203 is very complex , is much work.
Perhaps It's easier to take a LTC6912-1 (2 channel ,gain: 0,1,2,5,10,20,100) or an LTC6912-2 with gain 01,2,4,8,16,32,64),
and you need only a input stage(for dividing and protection with clamp-diodes) and a voltage spltter to 2x3.3V or 2x5V.
The LTC has also 3 wire SPI.
Yes, I know it's a bit more complex but if more bandwidth is needed it's the way to go :)
That LTC6912 seems a good choice, the main problem is the price/availability. The MCP6S92 I can ask for some samples to make some experiments, the LTC I don't know if they send samples... and it's $4+ on digikey...

Do you have a video with the 2 knobs setup?

mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Fri Sep 08, 2017 1:38 am

Rexanet,

now I have big problems - I think with the Adafruit_ILI9341_STM - lib. The SPI graphic functioned, but I can't activate other SPI
devices like MCP6S91/92 or MCP4822 (DAC). I reduced the speed to 9MHz and back to 36MHz, but with no success.
I tested it with "blue-Pill" and Maple-Mini - the same. -

I tested MCP6S91/92 on UNO with success.
(I think I prefer the S91 , because it's' a XOR function,they have only one output .
On the Ref-Input of the S91 I can change the offset ...)

It's for me more difficult to get the CP1017N opto-switches in the schematic from the DSO203 as the preamp LTC6912,
I can get it for 4.37 € by www.voelkner.de , I think it's a good price for 2 channels.
But the small layout could be a problem for me.

But I don't know if I have their the same problems with the SPI, ???

zmemw16
Posts: 1413
Joined: Wed Jul 08, 2015 2:09 pm
Location: St Annes, Lancs,UK

Re: DLO-138 OScope

Post by zmemw16 » Fri Sep 08, 2017 3:04 am

first thought can you get the 91 alone working on stm32 spi1 ?
next if that involved playing with the clock, mode & polarity settings or not, anyway move it to spi2
check it still works
restore the display to spi1
stephen

mausi_mick
Posts: 138
Joined: Fri Aug 12, 2016 1:40 pm

Re: DLO-138 OScope

Post by mausi_mick » Fri Sep 08, 2017 8:28 am

It has worked in April, but now MCP6S91 worked alone, but not with the TFT-lib.
I have the same problem with the MCP4812/22 (SPI-DAC) and changed therefore to a I2C version (MCP4725?).
I tried different frequencies ( 9MHz, 10 MHz, 20MHz and 36MHz) for the MCPs and 36 MHz for the ILI9341.

But i don't know what I have changed in the programs meanwhile. Perhaps its a problem with the Arduino IDE (going from 1.6.3 to 1.84) or the newest STM32 - lib ?

User avatar
rexnanet
Posts: 203
Joined: Wed Mar 16, 2016 10:34 am

Re: DLO-138 OScope

Post by rexnanet » Fri Sep 08, 2017 8:45 am

mausi_mick wrote:
Fri Sep 08, 2017 1:38 am
Rexanet,

now I have big problems - I think with the Adafruit_ILI9341_STM - lib. The SPI graphic functioned, but I can't activate other SPI
devices like MCP6S91/92 or MCP4822 (DAC). I reduced the speed to 9MHz and back to 36MHz, but with no success.
I tested it with "blue-Pill" and Maple-Mini - the same. -

I tested MCP6S91/92 on UNO with success.
(I think I prefer the S91 , because it's' a XOR function,they have only one output .
On the Ref-Input of the S91 I can change the offset ...)

It's for me more difficult to get the CP1017N opto-switches in the schematic from the DSO203 as the preamp LTC6912,
I can get it for 4.37 € by www.voelkner.de , I think it's a good price for 2 channels.
But the small layout could be a problem for me.

But I don't know if I have their the same problems with the SPI, ???
Hi mausi_mick,

CP1017N I´m going to get from aliexpress, 3.21€ for 10 pieces : https://www.aliexpress.com/item/Free-Sh ... 38858.html
It's not fast but it seems to be a good price...

That point on offset with the S91 is a good point.
I was thinking on S92 to allow to have 2 channels @ 1MSPS or 1 channel @ 2MSPS.

I think that your problems might be related to an Adafruit_ILI9341_STM lib update (without any certainty). I have faced some problems on other platforms (ESP32 and ESP8266) when upgrading this lib...
I have one Arduino IDE for each platform to avoid upgrading problems...
It might be related to CS activation and de-activation.
If you send me the code I can have a look.

Post Reply