Spot The Mistakes

Hardware PCB
1

Hi all,
I’ve been working on a new pcb for use by myself and to supply as a ‘box’ to a couple of local farmers without the electronics skills to build their own PCBs. It is based around a single USB input, with an integrated hub IC to provide USB to MPCIe modem and GPS modules, a CH340 for the arduino and a spare output for future expansion. 12v power is also supplied to the tablet for charging (The Chuwi range of tablets run directly off 12v). The power stage is designed for hydraulic valves, with 2 direction coils and a solenoid valve which cuts flow to the valve for safety. There is also a PCA9685 for I2C comms with a separate CMPS14 module. All SMD components.

I think I have completed the schematic but I’m bound to have made some errors. So to those more skilled than myself, thank you in advance for taking the time to critique my work :slight_smile:
I will post updates and gerber files as the schematic is finalised and routing is done, in case anyone else wants to build this project.

4 Likes
2

Yup that’s my plan too after I build my own and see it in action. Lots of interest in AOG if it works well and has local tech support.

3

Hi to all
Hope everybody is staying away from the virus
I got the board mostly built and thought I could see if I get any connection.
On the main screen it says connected
In the ports area where it shows message from steering module
It says “waiting for agopen”
I looked at the code and there is mention of Waiting for agopen”
Can someone tell me what this means?
Could it mean I don’t have gps hooked up yet
Could it make mean my inclinometer or
Analogue to digital converter not working

4

It means the Arduino is waiting for AoG to send it some data

5

Make sure you have the simulator on if not got gps hooked up

6

And WAS

@CQuick PCA9685 better than PCA9615?

7

@Vili Meant to say 9615. 9685 is a 16 channel pwm chip that I’ve also been thinking about

8

Thanks
Will try that this morning

9

You’re using a Nano module, right? In that case, you’ll have two drivers on its RxD line: U10 and the same IC on the Arduino Nano module.

10

Yes
Same as using any other serial device on those pins?
It works, anyway :slight_smile:

11

nice to hear. yes, same issue. Fortunately, low side drivers are often a little bit stronger :+1:

12

In the “IMU differential comms” part, which type of resistor do you mount ?

In the schematic there are 390 ohm and 100 ohm resistor.

The roof unit is the same schematic with CMPS14 mount header ?

13

Yeah those are the impedance matching resistors, and pullups and pulldowns for the bus.
100R is approximately the characteristic impedance of Cat 5e. The 390R pullups/downs are if anything a little bit strong but it seems to work. Those values are used in the Sparkfun board, the datasheet specified 600R. I might simplify the BOM for version 2 and go with 470R.

The same matching network needs to be present at both ends of the bus for it to work, so the schematic is identical at the CMPS14 end

14

RJ45 is for indoor use.

If i use M12 4 pin connection, can it work ?

rj45 to m12
RJS-12D04FM-RS8001.pdf

15

You need at least 6 pins for it to work - power, ground, DSDAP, DSDAM, DSCLP, DSCLM.

You need the 100R resistor on the board itself, as the pca9615 samples the signal on either side of the resistor. The datasheet has a good explanation on the resistor network and how to implement it
image

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https://www.delock.com/produkte/G_66314/merkmale.html?setLanguage=en

Delock 66314 : M12 8 pin to rj45 8 pin, IP67 rated.

17

I’ve changed a few things around following testing of the v1 board.
If anyone’s interested, the gerber files and bom for my main board and CMPS module are attached.
main.zip (496.6 KB)
cmps_breakout.zip (82.1 KB)

3 Likes
18

That looks fantastic I have just started on this site and really appreciate the positive knowledge base that everyone has to continuous improvement

19

Been working on ethernet based modules for v3
Started with the IMU as it’s the simplest.
I’ve attached the gerbers and PDF - Please let me know what you think. I’m completely new to working with ethernet so I’ve probably committed some cardinal sins regarding the routing, impedance matching, etc.

Thank you to anyone who takes the time to look at these, I really appreciate all feedback!

IMU.pdf (61.0 KB)
gbr.zip (131.0 KB)

1 Like
20

Im also a newbie looks good to me