The flash chip on my board is an ISSI IS26LP256P chip. The ISSI chip
requires slightly different setup for quad mode from the other brands,
but works fine with the existing SPI flash interface logic here.
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
top-orangecrab0.2 is a copy of top-arty with various changes.
USRMCLK is added for the SPI clock
ethernet is removed
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
A first pass at ghdl synthesis using yosys and nextpnr. It runs hello world
or micropython if the FPGA has enough block RAM (eg ECP5 85F). The hello
world testcase also loops UART rx to tx in software (ie not a hardware
loopback).
It uses Docker images, so no software needs to be installed. If you prefer
podman you can use that too. Edit Makefile.synth to configure your FPGA,
JTAG device etc.
To build:
make -f Makefile.synth
and to program:
make -f Makefile.synth prog
A few issues:
We need to add PLL support. Right now Microwatt runs at whatever the
external clock frequency is and the baud rate gets scaled by how far off
50MHz it is. This means on the ecp5-evn with a 12 MHz clock rate the baud
rate is a quite strange 27650 (115200 * 50 / 12). On my OrangeCrab with a
50MHz clock the UART is 115200.
It uses a large amount of resources, way more than it should. There are
still some ghdl/yosys issues to be sorted out.
Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
Paul Mackerras
Matt Johnston