Saturday, March 22, 2014

Sparkfun Bus Pirate issue found!

Spurred on by the LCD success,  the next Project was an FNP1500-48 1500W 48V power supply that I got off ebay to power my 700W HF amplifier. It was much smaller and lighter than my Lambda 48V 32A power supply. It was originally intended to be mounted in a chassis along with other identical modules with an LCD as a server power supply and therefore had an I2C Interface. This could be investigated with the Bus Pirate. I found the manual online for the power supply and also the IIC specification.
First a connector for the 20 pin connector on the supply was needed. This was constructed on a piece of stripboard with four 5 pin female 0.1" female connectors Gorilla glued in place. I connected leads to the SCL SDA and Gnd and powered up the power supply. Nothing, even after moving the recessed switch on the front panel from "0" to "1". Re reading the manual, more carefully Pin R1 and S5 have to be connected to activate the power supply. This worked and the power supply produced 49.8V output. Time to hook up the Bus Pirate

I had a Seed studio Bus Pirate Probe kit which breaks out the 10 pin connector to 10 mini hooks. Using the colour scheme of the bus pirate IIC,  v command.

1.(BR)  2.(RD)  3.(OR)  4.(YW)  5.(GN)  6.(BL)  7.(PU)  8.(GR)  9.(WT)  0.(Blk)
GND     3.3V    5.0V    ADC        VPU     AUX     SCL     SDA      -            -

 I hooked up the appropriate pins (1& 7&8) , with 10K pullup resistors I started bus pirate. This has a macro for searching for IIC addresses.  Ran the macro, found nothing. Did not see anything in or out on my $20 oscilloscope, so I started looking at voltages again. I noticed that 5V appeared between pins 0 and 9 on cable plugged into  the Sparkfun board. Was the connector on the Sparkfun board flipped?. I went to the web and looked at the board pictures


Spot the difference? The seed studio board has the notch on the connector away from the edge of the PCB whereas the Sparkfun board has the notch on the PCB edge of the connector. This explains the problem. Luckily the plastic housing on the sparkfun board is not glued down, it lifts off and could be made to match the seedstudio unit.. Hooked up the power supply and ran the IIC scan and found the IIC addresses as listed  in the manual.

Bus Pirate v3.a
Firmware v6.1 r1676  Bootloader v4.4
DEVID:0x0447 REVID:0x3046 (24FJ64GA002 B8)
HiZ>m                                         <change mode
1. HiZ
2. 1-WIRE
4. I2C
5. SPI
6. 2WIRE
7. 3WIRE
8. LCD
x. exit(without change)

Set speed:
 1. ~5KHz
 2. ~50KHz
 3. ~100KHz
 4. ~400KHz

Pull-up resistors ON
Searching I2C address space. Found devices at:
0xBE(0x5F W) 0xBF(0x5F R)

Perhaps the Sparkfun unit connector is deliberately missorientated so you cannot run their competitors accesories? We will see their response! (update: they claim they didn't and they didn't know of the issue, but posts on their web page for their buspirate raised the issue 3 years ago!)

Going back to the LCD Interface this no longer worked properly. So I connected it up with the original cable seedstudio supplied. It worked. Obviously it was the sparkfun connector orientation issue again

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