Re: USB/BT GPS receiver connection problem

John wrote:
I'll add to what I just said.

I just looked at the specs, and it is definitely sending TTL serial
data throught the mini-USB connector. In that respect it is very
similar to the Holux 236. You can use a standard USB cable to charge
the device, but you need the adapter cable if you want to connect it to
a non-bluetooth computer.


I don't think there is any such thing as "TTL serial data", those are two different things. Holux is using the USB D+ and D- pins (which would normally be a TTL data pair) as a connection for the RS-232 serial TXD/RXD pair. The details are here:

http://www.holux-uk.com/Downloads/GPSlim236%20Manual-E.pdf

and here:

http://pinouts.ru/Slots/USB_pinout.shtml

The Holux manual shows the 236 has the RS-232 serial output (TXD and RXD) on the mini-USB connector on the receiver. And it shows there are three optional cables for the 236.

The "GR230-A1(RS232 data cable)" has a mini USB on one end and a DB-9P on the other for connecting to a hardware COM port. The manual does not say it but this cable can only transfer data, it can't provide power because hardware COM ports don't have +5VDC on them.

The "GR230-A2 (USB data cable)" has mini USB and USB A connectors and a "snake swallowing rabbit" housing molded into the cable that (I assume) houses the hardware of a serial to USB adapter. This cable (by itself, without the receiver connected) needs to have drivers installed for it before it can be used. That is the standard process for using serial to USB adapters, it is the process that results in a virtual COM port being created for use by applications looking for NMEA data.

The hardware in the serial to USB adapter needs the 5VDC power from the USB port to work, I assume it is also passing the 5VDC power on to the receiver and that this cable will charge the battery when it is in use.

The third cable, the GR230-A3 (Mini USB port to PS2 port), is not shown or discussed in the manual at the link. I assume it uses any one of the family of PS2 to DC adapter and PDA connectors (like those used for the mouse style cabled GPS receivers) to allow the 236 to get power from a DC adapter and communicate with a PDA by RS-232 serial connection.

A standard USB cable has a TTL data pair, not a RS-232 serial pair. I don't know what would happen if you took a standard USB A to mini USB cable and connected the 236 to a USB port. You would be connecting the serial RXD/TXD pair on the GPS to the D+ and D- pins of a normal USB port. It would probably provide charging power to the 236, it would not provide a serial connection, and I don't know if it puts any of the hardware on either end at risk of damage.

It would be careless of Holux to use a common connector in a manner that could easily result in damage from using the wrong cable. So I'm thinking that connecting a 236 to a USB port with a standard cable would not cause any dame or problems but I'm not sure of that.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)
.

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