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by vthielen
Fri Oct 31, 2014 10:53 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: UART RTS on B+
Replies: 3
Views: 1824

Re: UART RTS on B+

I used gpio_list (https://github.com/rewolff/bw_rpi_tools/tree/master/gpio) to check, and GPIO17 is on ALT3, as I wanted it to be. I guess the problem is that the UART's RTS is not doing what I expect (going high during transmit), but rather, it is used as an indication to another device that it is ...
by vthielen
Thu Oct 30, 2014 4:00 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: UART RTS on B+
Replies: 3
Views: 1824

Re: UART RTS on B+

Thanks for the help. I have used gpio_alt (http://www.raspberrypi.org/forums/viewtopic.php?f=44&t=39138) to swith pin 17 to ALT3, but I still don't see gpio17 move when I transmit. I am using the following code in python: #!usr/bin/python from pymodbus.client.sync import ModbusSerialClient as Modbus...
by vthielen
Thu Oct 30, 2014 2:06 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: UART RTS on B+
Replies: 3
Views: 1824

UART RTS on B+

I am trying to us the python pymodbus library on a RPI B+. I am using the SN65HVD12D chip as a RS485 driver, but this chip needs to be switched between receive and transmit. I think that, in the default configuration, the UART (coming out on GPIO 14 and 15) does not have the RTS signal to show when ...
by vthielen
Tue Sep 02, 2014 8:32 am
Forum: HATs and other add-ons
Topic: USB current capacity improvement
Replies: 11
Views: 2839

Re: USB current capacity improvement

I have had a look at the board and the datasheet of the U13 limiter chip (AP2553W6). If I change the R4 resistor, that is switched by the Q4 FET, from 39K to 15K, then the current limit (when max_usb_current=1 in the config file) should go up from 1.2A to about 2A. This should be sufficient I hope. ...
by vthielen
Fri Aug 29, 2014 6:34 am
Forum: HATs and other add-ons
Topic: USB current capacity improvement
Replies: 11
Views: 2839

Re: USB current capacity improvement

Redhawk: which 3G modem are you using? Are you feeding it straight off the RPIB+ USB, or off a powered hub? How many times per day does it auto-reconnect? (if any) Maybe yours works more stable because it has a 3.3V internal linear regulator and the internal electronic don't see the external voltage...
by vthielen
Thu Aug 28, 2014 12:40 pm
Forum: HATs and other add-ons
Topic: USB current capacity improvement
Replies: 11
Views: 2839

Re: USB current capacity improvement

The modem is a huawei HSDPA (E173) modem. The 2 amp is very short (1ms), I guess the Chinese didn't want to put a large capacitor inside and where counting on there being one on the other side of the USB port :-)
by vthielen
Thu Aug 28, 2014 11:58 am
Forum: HATs and other add-ons
Topic: USB current capacity improvement
Replies: 11
Views: 2839

Re: USB current capacity improvement

I already added a 1000uF elco, but that seemed to make matters worse. I put it on the scope, and with the additional 1000uF, minimum voltage (during dip) went from 3.3 to 4V Maybe I get more fails with the elco because the dips become wider? I don't want to put a bigger elco, because the USB port mi...
by vthielen
Thu Aug 28, 2014 11:31 am
Forum: HATs and other add-ons
Topic: USB current capacity improvement
Replies: 11
Views: 2839

USB current capacity improvement

Hello, I am using the B+ with a GSM modem USB stick. This stick can draw very large current pulses from the USB port (2A during 1ms), during which the voltage on the USB port can go down from 5 to 3.3V, evidently causing some problems in the link (wvdial drops regularly) I already changed the config...
by vthielen
Tue Jul 15, 2014 12:49 pm
Forum: General discussion
Topic: The Raspberry Pi Model B+ Q&A thread
Replies: 388
Views: 177234

Re: The Raspberry Pi Model B+ Q&A thread

Will it be possible to turn power to the USB ports off?
I am having problems with a USB GSM modem and the only way to reset it is to turn it off and on again?
I think this is not possible on the normal model B?
by vthielen
Wed Mar 05, 2014 10:21 am
Forum: General discussion
Topic: Need for Industrial Quality RPi System
Replies: 27
Views: 9929

Re: Need for Industrial Quality RPi System

I am currently developing a protection system, which needed a Human Machine Interface. This HMI does: - communication over a serial link with an MCU that does the actual critical protection function. - touch-screen access - Ethernet link. I thought of using a RPI, but chose another platform in the e...

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