Streamer "gotcha" and INB issue
ozpropdev
Posts: 2,791
in Propeller 2
Hi Chip
I've encountered a couple of issues while using the streamer.
The "gotcha" was an example of incorrect use by me of the hub FIFO.
In the P2 documentation the following statement is made.
Maybe an additional warning needs to be added to the docs along the lines of:
This had me wheel spinning (or should that be cog spinning) for a while
The second issue I found was when trying to capture the top 8 bits of INB, the
lower nibble is incorrect. Diving into it deeper I discovered that the same issue occurs
when reading INB. Pins 59..56 outputs work OK but can't be read.
The code below was used to test all pins.
Brian
I've encountered a couple of issues while using the streamer.
The "gotcha" was an example of incorrect use by me of the hub FIFO.
In the P2 documentation the following statement is made.
There are three ways the hub FIFO interface can be used, and it can only be used for one of these, at a time:
Maybe an additional warning needs to be added to the docs along the lines of:
You CANNOT issue a WRFAST instruction while in hubexec mode.
This will cause code execution to cease.
This had me wheel spinning (or should that be cog spinning) for a while
The second issue I found was when trying to capture the top 8 bits of INB, the
lower nibble is incorrect. Diving into it deeper I discovered that the same issue occurs
when reading INB. Pins 59..56 outputs work OK but can't be read.
The code below was used to test all pins.
'toggle a pin an read its state back sys_clk = 80_000_000 led = 32 pin = 56 'pin to test dat org setb dirb,#led 'enable status led mov adra,#pin testb adra,#5 wc if_nc setb dira,#pin 'set pin as output if_c setb dirb,#pin .loop if_nc notb outa,#pin 'toggle pin if_c notb outb,#pin waitx ##sys_clk / 4 if_nc testb ina,#pin wz 'read pin if_c testb inb,#pin wz setbz outb,#led 'update status jmp #.loopCheers
Brian
Comments
In order to hook up more hardware to P0..P63, some pins' outputs and inputs go different places. In your case, P63 is reading the RX signal from the USB chip and P59..P56 are reading the three pushbuttons PB3..PB0.
I'm sorry this wasn't documented.
About the WRFAST during hub execution: That will blow things up, for sure. So should any of those related instructions. I'm adding a bit to the documentation now to cover this.
A quick look at the schematic shows a 10K pullup on the push buttons.
I assumed outputting to those pins would be OK.
What tricked me was the fact that P59..P56 on the header show the expected waveforms on the scope.
Looking at the schematic again I now see that P59.P56 have dual assignments on the FPGA.
It appears that outputs for these pins is on the header and the inputs are mapped to the push buttons.
It all makes sense now...:)
Cheers
brian