Jaguar Brake/coast

[pauldemonkey]

We are trying to get a jaguar to brake and can't figure out exactly how to wire it. I saw one thread about a pulldown resistor and two wires in the sidecar with only one in the jaguar, if we are supposed to do it that way then how exactly should it be wired and how big of a resistor do we need?

[bladetech932]

Getting the jaguar to brake just involves moving the farleft two pin jumper to the b side
.From....- -
.........b...c
..to.....- -
.........b...c

[Al Skierkiewicz]

You can wire a digital output to the brake jumpers and control brake from software if you like.

[Kyledoo]

Originally Posted by Al Skierkiewicz

You can wire a digital output to the brake jumpers and control brake from software if you like.

and how would you do this? which ports on the sidecar would you use and which wires get connected? do you use 3 wire cables or 2 wire? I get the concept but don't quite understand how it would be implemented. we would be interested in doing this so it can be on brake during auto mode and coast during teleop. we are using victors, but i assume the process is the same

[Al Skierkiewicz]

Kyle,
You would wire to a digital output but only use the black and white wires. Black to pin 3 and white to pin 2 on the Jag. The +5 volt line is not used. It appears that the jumper input on the Jag for coast and brake is either tied to +3.3 volts or power common. The data sheet for the controller chip does not seem to pull this input high so a pullup resistor (1k) from the Jag 3.3 volt pin (pin 1) to the center pin (pin 2) would likely be needed. Then simply program a digital output to be low for "brake" and high for "coast". we have used a similar method on Victors in the past but do not use Jaguars.

[heydowns]

If using CAN, you can also control Brake/Coast via software directly by issuing commands over the CAN bus.

[rwood359]

Originally Posted by Al Skierkiewicz

Kyle,
You would wire to a digital output but only use the black and white wires. Black to pin 3 and white to pin 2 on the Jag. The +5 volt line is not used. It appears that the jumper input on the Jag for coast and brake is either tied to +3.3 volts or power common. The data sheet for the controller chip does not seem to pull this input high so a pullup resistor (1k) from the Jag 3.3 volt pin (pin 1) to the center pin (pin 2) would likely be needed. Then simply program a digital output to be low for "brake" and high for "coast". we have used a similar method on Victors in the past but do not use Jaguars.

The following is from the FAQ on Luminary Micro. Only the white wire on the DS DO needs to be connected to the center pin on the B/C connector. We are currently using this. The driver likes coast going over the bump and brake on the level field.
http://www.luminarymicro.com/jaguar

Brake/Coast Interface
Q
What is the best connection for a dynamic brake/coast interface?
A
If you are using the CAN interface, the brake/coast jumper setting may be overridden, and therefore no electrical interface to the brake/coast pins is necessary.
Otherwise, if you are using a PWM (servo) interface, you can connect just the center pin of the brake/coast header to a digital source (e.g. for FRC users the digital side car). Note that you shouldn’t hook up a ground signal because you do not want this to act as a current return path to the battery. You want the current return path exclusively through the V‐ screw terminal.

[Al Skierkiewicz]

I wonder if this applies to old Jaguars or just the new models. The schematic I have for last year's model does not show any pullup for selection. The jumper is connected to +3.3 volts in one position or power supply common in the other.

[The Lucas]

I have made these brake coast cables cables before and if I remember correctly the rated max fanout for digital outs on the digital sidecar is 3. So if you have 4 speed controllers on the drive I recommend you daisy chain (or Y-cable) the left controllers to one digital output, then do the right controllers on a separate output. I have daisy chained one digital out to 4 speed controllers on a practice robot. It worked on all 4 controllers, but I wouldn't do this on your competition bot (use atleast 2 digital outs).

[Ether]

Originally Posted by Al Skierkiewicz

I wonder if this applies to old Jaguars or just the new models. The schematic I have for last year's model does not show any pullup for selection. The jumper is connected to +3.3 volts in one position or power supply common in the other.

I think the pullup is done by the NI 9403 sourcing digital output.

I sent a PM to Greg asking about this but haven't heard back yet.


~

[Al Skierkiewicz]

Ether,
In looking at the NI manual as a reference here...http://www.ni.com/pdf/manuals/374069e.pdf It shows an external pullup is needed and the sidecar has a 10k pullup to sidecar +5 volts. Kind of scary that way since there appears to be no protection to the input pin of the LM3S2616 in the Jaguar.

[Ether]

Originally Posted by Al Skierkiewicz

It shows an external pullup is needed

Al, can you reference the Page or Paragraph where it says an external pullup is needed? I didn't see any reference to external pullup.

Here's what I found:

According to the NI 9403 "c_series_do.pdf" document Page 1 Table 1:

the 9403 has 32 Sink/Source 5V/TTL inputs/outputs. Output is 5V @ 2 mA.


According to document "374069e.pdf" "OPERATING INSTRUCTIONS AND SPECIFICATIONS NI 9403 32-Channel, TTL Digital Input/Output Module", Page 7:

Each channel has a DIO pin to which you can connect a digital input or output device. The 32 DIO channels are internally referenced to COM, so you can use any of the four COM lines as a reference for the external signal. ... You can independently configure each DIO channel in software for input or output.


The Digital Sidecar (DS) connects to the NI 9403 module.

According to "3-2010FRCControlSystemComponent DatasheetsRev1_enc.pdf":

(Page 16 Para 3.4.1) Functional Description
The Digital Sidecar is a breakout module that is designed to adapt a single cRIO 9403 32-channel digital I/O module into a set of I/O that is familiar to robotics hobbyists.

(Page 16 Para 3.4.1.1) Features
The Digital Sidecar includes the following features:
- 14 general purpose I/O (aka GPIO) lines with available 5V power for each


(Page 18 Table)
J26 GPIO A 3x14 0.1” pin field for general purpose digital I/O with 5V available on the center pin, ground on the pin closest to the PCB’s edge and I/O signal on the pin furthest from the PCB’s edge.

(Page 19 Specifications)
GPIO – Pull-Ups 10 kOhms* these signals are passed directly to the NI 9403 module without any series resistance but include pull-ups to 5V

*I interpreted these as internal pullups since it says later in the sentence that they are included


~

[Dave Flowerday]

Originally Posted by Al Skierkiewicz

I wonder if this applies to old Jaguars or just the new models. The schematic I have for last year's model does not show any pullup for selection. The jumper is connected to +3.3 volts in one position or power supply common in the other.

My assumption would be that the input pin on the Jaguar MCU has a configurable internal pull-up that is enabled.

[Ether]

Originally Posted by Dave Flowerday

My assumption would be that the input pin on the Jaguar MCU has a configurable internal pull-up that is enabled.

According to the LM3S2616 data sheet Page 247, GPIO pins have programmable pull-up or pull-down resistors.


~

[Al Skierkiewicz]

Ether,
I was referring to Figure 2 on page 8.