BCD436HP/BCD536HP: Serial Access before USB Interface

[blantonl]

Does anyone know if there is internal serial access points (TX/RX pads) *before* the USB serial interface in the scanner?

I'm interested in interfacing an internal Bluetooth module into the 436 for serial control over bluetooth.

I've already done this for GPS functionality (TX/RX pads are clearly marked)

 

[jonwienke]

No. The only marked pads are for the USB jack connections power and data in/out. But except for the +5V power pad, they are under the metal shield around the USB jack and you'd have to have a black belt in solder-fu to work in the space under the shield, or else temporarily remove the shield to make the connections. You'd need a Bluetooth module that can interface directly with USB, and eliminating RFI is going to be a significant challenge.

 

[blantonl]

I'm actually referring to the serial data before it gets to the USB interface chip. I suspect it's outputted from the CPU in TTL format which would be perfect.

I'm already using an HC-05 Bluetooth module internally for the GPS TX/RX data and it works perfectly with zero RFI issues. It is paired with an HC-06 Bluetooth module that is installed in the back of the car interfaced with a uBlox GPS module. Internally in the 436 I tapped a power from one of the 3.3V marked pads... however I ended up putting a push button toggle switch on it because it appears that pad is always powered and drains the battery and prevents proper charging when always connected.

 

[jonwienke]

I haven't seen any obviously marked data pads other than the ones near the USB and GPS jacks.

 

[blantonl]

I bet there is an FTDI chip under the shield with the CPU. I might have to dig in there to have a look. The CPU is almost certainly sending TTL serial data to an FTDI USB serial chip. If I can intercept that TTL data before it gets to the USB chip, I can send it over bluetooth and then create a Ardunio based remote head over Bluetooth.

 

[jonwienke]

Good luck with that. The circuit board has 6 layers of traces (you can see them numbered at the bottom below the speaker pads), so unless you can desolder the relevant chip pins from the board and connect leads directly to the chips, you are probably better off finding a USB-Bluetooth module and wiring it to the pads near the USB jack.

 

[jonwienke]

You could probably use just about any USB bluetooth dongle, if you desoldered the USB plug and stripped the board out of the case.

 

[blantonl]

the FTDI chip requires a driver to operate - so any off the shelf USB-Bluetooth module won't know the relevant language to communicate with the FTDI chip to translate USB to serial. Same issue as if I was to interface a Ardunio board to the USB output - the Ardunio would need a driver for the FTDI USB/Serial interface and one doesn't exist for the Ardunio platform.

The FTDI chip, when found, has TX, RX and GND pins where we could tap there before the TTL signal goes in. I could tap it there, cut the pins, and we'd be set.

 

[jonwienke]

I thought some Bluetooth sticks just passed the serial data from the USB interface to the Bluetooth interface.

The biggest problem you will have is getting the 436 driver to link to a Bluetooth connection, regardless of how you connect the Bluetooth to the scanner.

 

[blantonl]

We won't need the 436 driver, because we would be bypassing the FTDI USB chip all together. The driver is for the FTDI USB to serial interface.

If we can intercept the TTL output from the CPU, a simple TTL to RS-232 level converter connected to the bluetooth module is all that is needed. Then, either a PC could pair with the bluetooth module and expose a simple serial port, or a slave Bluetooth module could be configured to pair with the scanner's bluetooth and then provide serial data for custom applications (such as a Ardunio based remote head etc)