mesa_modbus: Document fault and rate limiting pins, fix some pin name formats

Signed-off-by: andypugh <andy@bodgesoc.org>

Author: andypugh

docs/src/drivers/mesa_modbus.adoc

@@ -135,9 +135,38 @@ module will create the following pins for each instance of the driver:
 
 *modname.drive_delay* (default 0)
 
+•modname.update-hz* (default 0)
+
+*modname.fault* - indicates a fault with the device or comms
+
+*modname.last-error* - indicates the error code that set the fault
+output.
+
 These can be redefined at any time and will take effect the next time
 that a modbus packet is assembled.
 
+*modname.update-hz* is provided to slow down the transaction rate for
+modbus devices that become unstable if polled too frequently. If you see
+fault 11 then try setting this to 0.1Hz or even 1Hz. If set to zero the
+system runs as fast as it can.
+
+The fault codes returned in "last error" are
+
+|===
+|Code|Fault
+|1|Illegal Function
+|2|Illegal Data Address
+|3|Illegal Data Value
+|4|Server Device Failure
+|5|Acknowledge
+|6|Server Device Busy
+|7|Negative Acknowledge
+|8|Memory Parity Error
+|9|Gateway Path Unavailable
+|10|Gateway Failed to Respond
+|11|Comm Timeout
+|===
+
 Each module exports a single HAL function to be attached to a realtime
 thread. The function name is just the module name, with no distinction
 made between read and write cycles.

src/hal/drivers/mesa-hostmot2/modbus/mesa_modbus.c

@@ -347,8 +347,8 @@ int rtapi_app_main(void){
                                     i, channels[c].name);
                                 retval = hal_pin_float_newf(HAL_IN,
                                     (hal_float_t**)&(inst->hal->scale[p]),
-                                    comp_id, COMP_NAME".%02i.%s-%02i-scale",
-                                    i, channels[c].name, j);
+                                    comp_id, COMP_NAME".%02i.%s-scale",
+                                    i, channels[c].name);
                                 retval = hal_pin_float_newf(dir,
                                     (hal_float_t**)&(inst->hal->pin2[p]),
                                     comp_id, COMP_NAME".%02i.%s-scaled",
@@ -380,11 +380,11 @@ int rtapi_app_main(void){
                                 retval = hal_pin_float_newf(HAL_IN,
                                     (hal_float_t**)&(inst->hal->scale[p]),
                                     comp_id, COMP_NAME".%02i.%s-scale",
-                                    i, channels[c].name, j);
+                                    i, channels[c].name);
                                 retval = hal_pin_float_newf(HAL_IN,
                                     (hal_float_t**)&(inst->hal->pin2[p]),
                                     comp_id, COMP_NAME".%02i.%s-offset",
-                                    i, channels[c].name, j);
+                                    i, channels[c].name);
                             }
                             *(inst->hal->scale[p]) = 1;
                             p++;