Dreg has uploaded this change for review.
buspirate_spi: Add support for hiz output with pullups=off
When working with low-voltage chips, the internal 10k pull-ups of the Bus Pirate might be too high. In such cases, it's necessary to create an external pull-up using lower-value resistors. For this, you can use the ``hiz`` parameter. This way, the Bus Pirate will operate as an open drain
Change-Id: I6d9909b23782ef3fcb1428fd127dae0d6b211855
Signed-off-by: Dreg <dreg@rootkit.es>
---
M buspirate_spi.c
M doc/classic_cli_manpage.rst
2 files changed, 22 insertions(+), 2 deletions(-)
git pull ssh://review.coreboot.org:29418/flashrom refs/changes/99/79299/1
diff --git a/buspirate_spi.c b/buspirate_spi.c
index 72c28b0..7436d80 100644
--- a/buspirate_spi.c
+++ b/buspirate_spi.c
@@ -325,6 +325,7 @@
int spispeed = 0x7;
int serialspeed_index = -1;
int ret = 0;
+ bool hiz = false;
bool pullup = false;
bool psu = false;
bool aux = true;
@@ -368,6 +369,17 @@
}
free(tmp);
+ tmp = extract_programmer_param_str(cfg, "hiz");
+ if (tmp) {
+ if (strcasecmp("on", tmp) == 0)
+ hiz = true;
+ else if (strcasecmp("off", tmp) == 0)
+ ; // ignore
+ else
+ msg_perr("Invalid hiz state, not using them.\n");
+ }
+ free(tmp);
+
tmp = extract_programmer_param_str(cfg, "pullups");
if (tmp) {
if (strcasecmp("on", tmp) == 0)
@@ -692,9 +704,9 @@
/* Set SPI config: output type, idle, clock edge, sample */
bp_commbuf[0] = 0x80 | 0xa;
- if (pullup) {
+ if (pullup || hiz) {
bp_commbuf[0] &= ~(1 << 3);
- msg_pdbg("Pull-ups enabled, so using HiZ pin output! (Open-Drain mode)\n");
+ msg_pdbg("Pull-ups or HiZ enabled, so using HiZ pin output! (Open-Drain mode)\n");
}
ret = buspirate_sendrecv(bp_commbuf, 1, 1);
if (ret)
diff --git a/doc/classic_cli_manpage.rst b/doc/classic_cli_manpage.rst
index 5d6b7ef..3157793 100644
--- a/doc/classic_cli_manpage.rst
+++ b/doc/classic_cli_manpage.rst
@@ -763,6 +763,14 @@
where ``baud`` can be ``115200``, ``230400``, ``250000`` or ``2000000`` (``2M``).
The default is ``2M`` baud for Bus Pirate hardware version 3.0 and greater, and 115200 otherwise.
+When working with low-voltage chips, the internal 10k pull-ups of the Bus Pirate might be too high. In such cases, it's
+necessary to create an external pull-up using lower-value resistors. For this, you can use the ``hiz`` parameter.
+This way, the Bus Pirate will operate as an open drain. Syntax is::
+
+ flashrom -p buspirate_spi:hiz=state
+
+where ``state`` can be ``on`` or ``off``.
+
An optional pullups parameter specifies the use of the Bus Pirate internal pull-up resistors. This may be needed if you
are working with a flash ROM chip that you have physically removed from the board. Syntax is::
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